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AA-K178A-TK

1980

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Document:	Maintenance Operation Protocol Functional Specification
Order Number:	AA-K178A-TK
Revision:	000
Pages:	42
Original Filename:	http://decnet.ipv7.net/docs/dundas/aa-k178a-tk.pdf

OCR Text

(Phase Ill)
Maintenance Operation Protocol
I
Functional Specification
1'
(MOP)

Q r d No.
~ AA-K 178A-TK

software

DIGITAL Network Architecture
(Phase Ill)
Maintenance Operation Protocol
Functional S pecification
(MOP)
Order No. AA-K 178A-TK
Version 2.1.0

October 1980

This document describes the Maintenance Operation Protocol (MOP) functions, interfaces. messagas. and operation. MOP provides a set of messages and rules tor loading and dumping computw memory and testing a data link. MOP operates within a data link control procedure fnat
provides message framing and bit error detection. Although MOP is independent of any specific
data link control procedure. within the DIGITAL Network Architecture. the Digital Data Communicalions Message Protocol (OOCMP) 1s used for mat purpose.
This document provides technical information to assist those who implement the protocoi. It also
provides general information mat will enable others to evaluate MOP. The document assumes a
familiarity wtn computer communications. OOCMP. and OECnet. It is not intended to instruct those
unfamiliar with tnese concepts.

F i r s t Printing:

October 1980

T h i s m a t e r i a l may be c o p i e d , i n whole o r i n p a r t ,
provided t h a t t h e
c o p y r i g h t n o t i c e below is i n c l u d e d i n each copy a l o n g w i t h an
acknowledgment t h a t the copy d e s c r i b e s t h e ?9 p r o t o c o l developed by
D i g i t a l Equipment C o r p o r a t i o n .
T h i s material may be changed w i t h o u t n o t i c e by D i g i t a l Equipment
C o r p o r a t i o n , and D i g i t a l Equipment C o r p o r a t i o n i s n o t r e s p o n s i b l e f o r
any e r r o r s which may a p p e a r h e r e i n .

0
C

1980 by D i g i t a l Equipment C o r p o r a t i o n

The postage-prepaid READER'S COMMENTS t o r n on t h e Last page of t h i s
document r e q u e s t s t h e u s e r ' s c r i t i c a l e v a l u a t i o n t o a s s i s t us i n ?rep a r i n g S u t u r e documentation.
T'Â¥ EaLLow~nq a r e t r a d e m a r k s of D i q i c a l . Equipment C o r p o r a c ~ a n :

DIGITAL
OEC

POP
OECUS
UNIBUS
COMPUTER LABS

comx

DOT
DECCOMM
ASSIST- 11
VA X
DECnet
OATATRrSVE

wsaus

DECay stem- L O
DECtape
DIBOL
EDUSYSTSM

os/a

FLIP CHIP

RSTS

OMNIBUS

PHA

FOCAL

Rsx

INOAC

TYPESET-8
TYPESET- 11
TMS-11
ITPS-10
SBI
POT

LAB-8
OECSY STEM-20
RTS-8
VMS
IAS
TRA X

CONTENTS

Page
INTRODUCTION
FUNCTIONAL DESCRIPTION
Message Exchange
Storage Requirements
MOP Modes
I n i t i a t i n g Function Requests
Memory L o a d i n g
Memory Dumping
Link T e s t i n g
Unattended System C o n t r o l
Link Control Procedure
INTERFACE
Commands t o DDCMP
R e s p o n s e s f r o m DDCMP
MESSAGES
Message Format N o t a t i o n
MOP M e s s a g e F o r m a t s
Memory Load w i t h T r a n s f e r A d d r e s s
Memory Load w i t h o u t T r a n s f e r A d d r e s s
R e q u e s t Memory Dump
E n t e r MOP Mode
Request Program
R e q u e s t Memory Load
MOP Mode R u n n i n g
Memory Dump Data
R e s e r v e d f o r Remote-11 Use
R e s e r v e d f o r Remote-11 Use
P a r a m e t e r Load w i t h T r a n s f e r A d d r e s s
Loopback T e s t
Looped D a t a
OPERATION
MOP P r i m a r y a n d S e c o n d a r y Mode O p e r a t i o n
L o a d i n g Computer Memory
Dumpinq Computer Memory
Link T e s t i n g
Unattended C o n t r o l
MOP STATES, EVENTS, A N D ACTIONS
APPENDIX A
APPENDIX B
APPENDIX C
APPENDIX D

EXAMPLES
DDCMP MAINTENANCE MODE FORMAT
PROGRAM TYPES
REVISION HISTORY
TABLES

TABLE

1 Satellite State Table

TABLE 2 H o s t S t a t e T a b l e

ill

1.0

INTRODUCTION

T h i s document d e s c r i b e s t h e Maintenance O p e r a t i o n P r o t o c o l (MOP)
f u n c t i o n s , messages, and o p e r a t i o n . MOP l o a d s and dumps t h e memory of
an a d j a c e n t remote computer system v i a a p h y s i c a l communications l i n k ,
and t e s t s t h a t l i n k . MOP a l l o w s c o n t r o l o f u n a t t e n d e d remote s y s t e m s
t h a t a r e p a r t of a D E C n e t network.
MOP a l l o w s s e l e c t i o n and i n i t i a t i o n o f f u n c t i o n s from e i t h e r computer
on t h e l i n k .
These computer s y s t e m s a r e c a l l e d t h e h o s t and t h e
s a t e l l i t e . The h o s t implements t h e MOP f u n c t i o n s ; t h e s a t e l l i t e , t h e
t a r g e t of t h e h o s t , r e c e i v e s t h e l o a d , is t h e s o u r c e of t h e dump, and
l o o p s t h e t e s t messages back t o t h e h o s t .
I t is p o s s i b l e i n a DECnet
network f o r a h o s t t o g e t i t s l o a d images from a n o t h e r node o r f o r i t
t o send t h e dump t o a n o t h e r node f o r s t o r a g e .
MOP i s an o p t i o n a l

component of t h e DIGITAL Network A r c h i t e c t u r e
(DNA), t h e model upon which t h e DECnet p r o d u c t s a r e b u i l t . DECnet is
a f a m i l y of hardware and s o f t w a r e p r o d u c t s t h a t c r e a t e d i s t r i b u t e d
networks from DIGITAL computers and t h e i r i n t e r c o n n e c t i n g d a t a l i n k s ,
p e r m i t t i n g r e s o u r c e s h a r i n g and i n t e r p r o g r a m communication.

TheDNAmodel comprises
d i s t i n c t functions:

eight

layers

follows,

The P h y s i c a l Link Layer. The P h y s i c a l Link l a y e r
hardware i n t e r f a c e s t o s p e c i f i c system d e v i c e s .

each

with

its

provides

the

The Data Link Layer. The Data Link l a y e r manages communications
over a p h y s i c a l l i n k , u t i l i z i n g t h e D i g i t a l Data Communications
Message P r o t o c o l (DDCMP).
The T r a n s p o r t Layer. The T r a n s p o r t l a y e r r o u t e s messages between
s o u r c e and d e s t i n a t i o n nodes.
The Network S e r v i c e s Layer. The Network S e r v i c e s l a y e r manages
l o g i c a l d a t a c h a n n e l s , u s i n g t h e Network S e r v i c e s P r o t o c o l (NSP).
The S e s s i o n C o n t r o l Layer. The S e s s i o n C o n t r o l l a y e r p r o v i d e s
t h e system-dependent a s p e c t s o f l o g i c a l l i n k management, such a s
name-to-address mapping and a c c e s s c o n t r o l .
The Network A p p l i c a t i o n Layer.
The Network A p p l i c a t i o n l a y e r
p r o v i d e s 1/0 d e v i c e and f i l e a c c e s s . I t a l s o s u p p o r t s o t h e r
network f u n c t i o n s used by t h e two h i g h e r l a y e r s .
The Network Management Layer.
The Network Management l a y e r
p r o v i d e s user c o n t r o l over network p a r a m e t e r s and c o u n t e r s .
It
a l s o p r o v i d e s down-1 i n e l o a d i n g , up-1 i n e dumping, and t e s t ing
functions.
The User Layer.
programs.

The

User

layer

supports

user

services

and

o p e r a t e s w i t h i n t h e d a t a f i e l d of a d a t a l i n k c o n t r o l p r o c e d u r e
t h a t p r o v i d e s message framing ( l o c a t i n g t h e beginning and end of a
m e s s a g e ) , and b i t e r r o r d e t e c t i o n . T h i s is u s u a l l y provided by DDCMP,
b u t can be provided by hardware f a c i l i t i e s in some implementations.
MOP

Related documents are as follows:
DNA Data Access protocol (DAP) Functional Specifi-cation, Version
5.6.0, Order No. AA-Kl//A-TK
DNA Digital Data Communications
Message
Protocol
(DDCMP)
Functional Soecification, Version 4.1.0, Order No. AA-K175A-TX
DNA Network Management Functional Specification,
6rder No. AA-K181A-TK
DNA Network Services (NSP)
Order No. AA-K176A-TK

Functional

Version

2.0.0,

Specification,

Version

3.2.0,

DNA Session Control Functional
Order No. AA-K182A-TK

Specification,

Version

DNA Transport Functional Specification, Version 1.3.0,
AA-K180A-TK

Order

The following overview document for these specifications
introduction to the structure and functions of DNA.
DNA General Description, Order No.

AA-K179A-TK

1.0.0,

No.
an

2.0

FUNCTIONAL DESCRIPTION

MOP p r o v i d e s f i v e f u n c t i o n s :
MOP p r o v i d e s t h e c a p a b i l i t y f o r down-line
Load memory.
l o a d i n g t h e memory of a computer system. The o b j e c t of t h e load is t h e s a t e l l i t e system; t h e s o u r c e of d a t a is t h e h o s t
system.

Dump memory. MOP is used t o dump t h e c o n t e n t s
s y s t e m , u s u a l l y upon a f a i l u r e .

the

host

T e s t l i n k . MOP t e s t s t h e i n t e g r i t y of t h e d a t a l i n k and/or
i t s hardware components (modems and i n t e r f a c e s )
The h o s t
i n i t i a t e s t h e l i n k t e s t , and t h e s a t e l l i t e l o o p s back t h e
t e s t data.

F o r c e e n t r y i n t o t h e MOP mode. MOP is used t o h a l t c u r r e n t
s a t e l l i t e o p e r a t i o n and p u t t h e s a t e l l i t e i n t o MOP mode.
T h i s p r o v i d e s a means f o r t h e h o s t t o c o n t r o l an u n a t t e n d e d
s a t e l l i t e system.
MOP
T r a n s f e r c o n t r o l t o programs r e s i d e n t i n memory.
t r a n s f e r s c o n t r o l t o programs r e g a r d l e s s of whether t h e y a r e
loaded by MOP o r by o t h e r means.

2.1

Message Exchange

Host and s a t e l l i t e systems exchange messages o v e r a s i n g l e d a t a l i n k
i n a l t e r n a t e h a l f - d u p l e x mode.
Messages t r a v e l w i t h i n t h e D i g i t a l
Data Communications Message P r o t o c o l (DDCMP) message framing l i n k
c o n t r o l p r o c e d u r e e n v e l o p e , which p r o v i d e s d a t a i n t e g r i t y and e r r o r
MOP
d e t e c t i o n . Only messages w i t h no b i t e r r o r s p a s s t o MOP.
messages handle message acknowledgments and r e t r a n s m i s s i o n .

2.2

S t o r a g e Requirements

Whereas h o s t s must implement a l l MOP f u n c t i o n s , s a t e l l i t e s implement
o n l y what they a r e c a p a b l e of performing. B a s i c f u n c t i o n s r e q u i r e
v e r y l i t t l e code and may be coded i n t o read-only memories r e s i d e n t i n
A
primary mode e n a b l e s t h e s a t e l l i t e w i t h
t h e s a t e l l i t e system.
l i m i t e d amounts of read-on1 y-memory t o b o o t s t r a p i t s e l f up t o a
f u l l - f u n c t ion secondary mode.
I n a OECnet network, a h o s t may g e t i t s down-line
load images from
a n o t h e r node o r send i t s dump t o a n o t h e r node for s t o r a g e v i a DECnet
f u n c t i o n s . Thus l o a d i n g and dumpinq f u n c t i o n s can e x t e n d t o nodes
o t h e r than t h o s e d i r e c t l y connected t o t h e s a t e l l i t e .

2.3

MOP Modes

MOP o p e r a t e s i n two modes a s f o l l o w s :

Primary mode. Primary mode is used o n l y w i t h s a t e l l i t e s t h a t
A
ROM
contain
limited
amounts
of read-only memory.
c o n t a i n i n g o n l y MOP p r i m a r y code down-1 i n e
loads
the
secondary code i n t o t h e s y s t e m , b o o t s t r a p p i n g i t s e l f up t o
secondary mode.
The primary code s e n d s a Request Program Message t o t h e h o s t
and e x p e c t s i n r e t u r n a s i n g l e Program Load w i t h T r a n s f e r
Address Message c o n t a i n i n g t h e e n t i r e s e c o n d a r y code.
The s e c o n d a r y code is t h e n l o a d e d i n t o memory and s t a r t e d .

Secondary mode. Most f u n c t i o n s e x e c u t e i n s e c o n d a r y mode. A
s a t e l l i t e may s t a r t i n s e c o n d a r y mode e i t h e r by u s i n g a l a r g e
ROM c o n t a i n i n g t h e s e c o n d a r y code o r by l o a d i n g t h e s e c o n d a r y
code v i a a l o c a l l o a d d e v i c e such a s a c a s s e t t e .
Some f u n c t i o n s may r e q u i r e an even l a r g e r program t h a n can be
handled by t h e s e c o n d a r y code (which must be loaded i n a
s i n g l e m e s s a g e ) . I n t h e s e c a s e s , t h e s e c o n d a r y l e v e l program
is used t o l o a d t h e r e q u i r e d program f o r t h e r e q u i r e d
f u n c t i o n s ( a s is done f o r any l o a d memory r e q u e s t ) .

2.4

I n i t i a t i n g Function Requests

E i t h e r t h e h o s t o r t h e s a t e l l i t e can i n i t i a t e f u n c t i o n r e q u e s t s .
The
s a t e l l i t e i n i t i a t e s r e q u e s t s by s e n d i n g r e q u e s t messages t o t h e h o s t
( f o r example, t h e Request Program message and Request Memory Load
m e s s a g e ) . The h o s t i n i t i a t e s r e q u e s t s , a f t e r t h e s a t e l l i t e h a s s e n t a
MOP Mode Running Message, by s e n d i n g an a p p r o p r i a t e r e q u e s t command t o
t h e s a t e l l i t e ( f o r example, t h e Memory Load message and t h e Request
Memory Dump m e s s a g e ) . A l l message exchanges o p e r a t e one message a t a
time a l t e r n a t e l y between h o s t and s a t e l l i t e .

2.5

Memory Loading

Memory l o a d i n g can be i n i t i a t e d i n e i t h e r of t h e f o l l o w i n g ways.
The
c h o i c e depends on t h e i n i t i a t i n g computer and t h e p r e v i o u s f u n c t i o n
performed.
1.

The s a t e l l i t e s e n d s a Request Program message
t h e h o s t r e s p o n d s w i t h a Memory Load message.

the

host;

The h o s t s e n d s a Memory Load message t o t h e s a t e l l i t e w i t h o u t
having r e c e i v e d such a r e q u e s t .

Each l o a d i s numbered. The s a t e l l i t e acknowledges each l o a d w i t h a
Request Memory Load message r e q u e s t i n g t h e n e x t l o a d . The f i n a l load
is e i t h e r a Memory Load w i t h T r a n s f e r Address message o r a Parameter
Load w i t h T r a n s f e r Address messaqe. T h i s t r a n s f e r s e x e c u t i o n t o t h e
loaded proqram a f t e r loadinq any n e c e s s a r y r u n n ~ n q p a r a m e t e r s .

A f t e r t r a n s f e r , t h e new program may do one of t h e f o l l o w i n g :
1.

Continue t o run MOP.

Run a n o t h e r p r o t o c o l o r d a t a l i n k c o n t r o l
link.

Choose n o t t o use t h e l i n k a t a l l and run s t a n d a l o n e .

procedure

the

Thus, MOP may be e x i t e d f o l l o w i n g a t r a n s f e r t o a loaded program.

2.6

Memory Dumping

The h o s t always i n i t i a t e s memory dumping by s e n d i n g Request Memory
Dump message r e q u e s t s t o t h e s a t e l l i t e . The s a t e l l i t e r e s p o n d s w i t h
Memory Dump Data messages c o n t a i n i n g t h e r e q u e s t e d memory image. T h i s
p r o c e s s u s u a l l y c o n t i n u e s u n t i l t h e h o s t h a s completed t h e dump, a t
which time i t w i l l u s u a l l y s t a r t a memory l o a d o p e r a t i o n w i t h a Memory
Load m e s s a g e ( d e s c r ibed above)

2.7

Link T e s t i n g

The Loopback T e s t message t e s t s t h e l i n k . The a c t i v e s i d e s e n d s t h i s
message o u t on t h e l i n k , and w a i t s f o r i t s r e t u r n . The p a s s i v e s i d e
r e t u r n s a Looped Data message i f t h e message is looped from a
computer.
I f t h e message is looped from a loopback p l u g , modem
f a c i l i t y , o r o t h e r u n i n t e l l i g e n t loopback d e v i c e , t h e p a s s i v e s i d e
r e t u r n s a Loopback T e s t message. By moving t h e loopback p o i n t and
i s o l a t i n g components, t h e u s e r can d i a g n o s e problems. Upon r e c e i p t of
t h e r e t u r n e d message, t h e a c t i v e s i d e , knowing t h a t i t o r i g i n a l l y s e n t
t h e message, d o e s not r e t u r n i t .
Use o f t h e Looped Data messaqe
p r e v e n t s a s i t u a t i o n i n which two computers p a s s i v e l y loop t o one
a n o t h e r due t o t h e timing of a t e s t a b o r t .

2.8

Unattended System C o n t r o l

The E n t e r MOP Mode message, t o g e t h e r w i t h t h e a p p r o p r i a t e h a r d w a r e ,
e n a b l e s an u n a t t e n d e d s a t e l l i t e computer t o h a l t c u r r e n t o p e r a t i o n and
Control
begin e i t h e r MOP primary o r s e c o n d a r y mode o p e r a t i o n .
t r a n s f e r s t o a r e s i d e n t MOP program o r b o o t s t r a p . The hardware
r e c o g n i z e s t h e Enter MOP Mode message a n d " f o r c e s t h e computer system
t o t r a n s f e r c o n t r o l t o t h e MOP program. The password i n t h i s message
p r o t e c t s t h e system from being c o n t r o l l e d and
loaded
by
an
unauthorized h o s t .
S e c t i o n 5 d e s c r i b e s t h e MOP o p e r a t i o n i n c l u d i n g e r r o r r e c o v e r y .

2.9

Link C o n t r o l P r o c e d u r e

MOP o p e r a t e s w i t h i n t h e e n v e l o p e of a d a t a l i n k c o n t r o l p r o c e d u r e t h a t

provides
error-free
t r a n s m i s s i o n and r e c e p t i o n on a d a t a l i n k
his p r o c e d u r e p r o v i d e s
c o n n e c t i n g t h e h o s t and s a t e l l i t e s y s t e m s .
the following functions:
1.

Message framing.
Message framing i n v o l v e s l o c a t i n g t h e
beginning and end of a message a t t h e r e c e i v i n g end o f a
link.
T h i s p r o c e d u r e i n v o l v e s b i t , b y t e , and
message
synchronization.
MOP o n l y s e n d s and r e c e i v e s messages t h a t
a r e m u l t i p l e s of 8 - b i t b y t e s .

B i t eccoc d e t e c t i n g .

B i t e r r o r d e t e c t i o n is t h e d e t e c t i n g of
one o r more b i t e r r o r s i n t r o d u c e d by t h e communication
medium. Messages must be c o m p l e t e l y r e c e i v e d i n memory by
t h e l i n k c o n t r o l p r o c e d u r e and checked f o r e r r o r s b e f o r e t h e y
a r e passed t o MOP. Only good messages ( w i t h o u t b i t e r r o r s ) .
may be passed t o HOP. To s p e e d up e r r o r r e c o v e r y by a v o i d i n g
MOP w a i t i n g f o r t i m e o u t s , d a t a b i t e r r o r s can be f l a g g e d t o
MOP.

NOTE
I t is i m p o r t a n t t o have a d a t a l i n k
c o n t r o l r e c e i v e b u f f e r and t o p l a c e i t
s o t h a t i t w i l l n o t i n t e r f e r e w i t h MOP
operation.
I f a r e c e i v e b u f f e r is n o t
u s e d , a MOP l o a d message
will
be
directly
loaded
i n t o its s p e c i f i e d
a d d r e s s and t h e n checked f o r b i t e r r o r s .
I f t h e a d d r e s s is i n c o r r e c t , t h e image
w i l l be loaded i n t h e wrong p l a c e ,
destroying other information.

Turning around h a l f - d u p l e x
links,
and
selecting
and
addressing
multipoint stations.
The d a t a l i n k c o n t r o l
p r o c e d u r e p r o v i d e s any t i m e r s n e c e s s a r y f o r t h e s e o p e r a t i o n s .
The t i m e r s a r e t r a n s p a r e n t t o MOP. MOP t r a n s m i t and r e c e i v e
commands ( S e c t i o n 3 ) t r i q q e r s e l e c t i o n of a s t a t i o n and
t u r n i n g around of t h e l i n k . MOP h a s no s p e c i f i c l i n k c o n t r o l
commands. However, MOP may o p t i o n a l l y h a n d l e modem c o n t r o l
signals
d i r e c t l y , i f t h e y a r e passed through t h e MOP
i n t e r f a c e by t h e l i n k c o n t r o l p r o c e d u r e .
4.

Error recording.
The l i n k c o n t r o l p r o c e d u r e
e r r o r s , b u t is n o t r e q u i r e d t o p a s s them t o MOP.

may

record

The l i n k c o n t r o l p r o c e d u r e t y p i c a l l y h a s a s p e c i a l MOP mode t h a t
p r o v i d e s t h e above f u n c t i o n s .
T h e r e must be ways of e n t e r i n g and
e x i t i n g t h i s mode, and t h e mode can o p e r a t e more simply t h a n o t h e r
l i n k c o n t r o l modes a t t h e c o s t of performance. The ODCMP F u n c t i o n a l
S p e c i f i c a t i o n p r o v i d e s a d e t a i l e d d e s c r i p t i o n of how t h e D i g i t a l Data
Communications Message P r o t o c o l p r o v i d e s t h e s e f u n c t i o n s .
Within OECnet, MOP o p e r a t e s i n t h e d a t a l i n k l a y e r of t h e D i g i t a l
Network A r c h i t e c t u r e ( D N A ) . The d a t a l i n k c o n t r o l p r o c e d u r e provided
i n DNA is t h e D i q i t a l Data Communications Messaqe P r o t o c o l ( D D C M P ) .

3.0

INTERFACE

T h i s s e c t i o n d e s c r i b e s how MOP i n t e r f a c e s t o t h e d a t a l i n k c o n t r o l
procedure used f o r framing and e r r o r d e t e c t i o n . I t u t i l i z e s DDCMP a s
an example of such a d a t a l i n k p r o c e d u r e . R e f e r e n c e s t o DDCMP imply a
r e f e r e n c e t o t h e a c t u a l d a t a l i n k p r o c e d u r e used.
The i n t e r f a c e between MOP and DDCMP c o n s i s t s of a number of commands
t o DDCMP and r e s p o n s e s from DDCMP used t o t r a n s m i t and r e c e i v e MOP
messages t o and from t h e d a t a l i n k .
The a c t u a l i n t e r f a c e depends
h e a v i l y on t h e f e a t u r e s and c a p a b i l i t i e s w i t h i n t h e o p e r a t i n g s y s t e m s
running MOP and DDCMP.
Mechanisms used f o r p a s s i n g commands and
r e c e i v i n g r e s p o n s e s might i n c l u d e s h a r e d t a b l e s , c a l l s w i t h p a r a m e t e r
l i s t s , 1/0 r e g i s t e r s , and/or i n t e r r u p t mechanisms.
Its
The i n f o r m a t i o n passed between MOP and DDCMP a r e messages.
d e s c r i p t i o n u s u a l l y c o n s i s t s of a s t a r t i n g b u f f e r a d d r e s s and a l e n g t h
o r b y t e c o u n t , o r a c h a i n o f a d d r e s s e s and c o u n t s .

3.1

Commands t o DDCMP

ENTER MAINTENANCE MODE
T h i s command i n i t i a l i z e s DDCMP i n t o t h e maintenance mode b e f o r e
t r a n s m i t t i n g o r r e c e i v i n g maintenance mode messages. T h i s is t h e
s p e c i a l mode used f o r MOP o p e r a t i o n .
I f a MOP message i s
r e c e i v e d w h i l e n o t i n t h i s mode t h e p r o t o c o l w i l l h a l t , inform
t h e u s e r t h a t such a message was r e c e i v e d , and a l l o w t h e u s e r t o
r e s t a r t t h e p r o t o c o l i n t h i s mode v i a t h e E n t e r Maintenance Mode
command.
TRANSMIT MESSAGE
T h i s command g i v e s a message t o DDCMP
maintenance mode.

for

transmission

the

RECEIVE MESSAGE

T h i s command g i v e s an empty b u f f e r t o DDCMP f o r r e c e p t i o n of t h e
n e x t maintenance message.
A l t e r n a t e l y , MOP might s u p p l y DDCMP
w i t h a pool of b u f f e r s and have t h e p r o t o c o l s e l e c t one. I n t h i s
mode t h e r e w i l l be a command t o r e t u r n empty b u f f e r s t o t h e pool
f o r r e a s s i g n m e n t by DDCMP.
HALT PROTOCOL

T h i s command s t o p s t r a n s m i s s i o n and
reception
by
DDCMP.
O p t i o n a l l y , t h e r e may be a way t o c o n t r o l t h e modem s i g n a l s and
f o r c e t h e modem t o hang up i n t h e d i a l c a s e .
The p r o t o c o l may
a l s o h a l t by r e c e i v i n g a maintenance mode message w h i l e in normal
mode o r by r e c e i v i n g a normal mode message w h i l e in t h e
maintenance mode.
A f t e r h a l t i n g , t h e p r o t o c o l may be s t a r t e d
a g a i n i n t h e maintenance mode o r i n t h e normal mode.

3.2

Responses from DDCMP

MESSAGE TRANSMITTED
Response t o t h e T r a n s m i t Message command. The message has been
s e n t o u t on t h e l i n k .
The r e s p o n s e is r e t u r n e d a f t e r a c t u a l
t r a n s m i s s i o n is completed and i n c l u d e s any d e l a y
due
to
s e l e c t i o n , l i n k t u r n a r o u n d , and t r a n s m i s s i o n time.
MESSAGE RECEIVED
The n e x t maintenance message h a s been r e c e i v e d .
E i t h e r MOP
s u p p l i e d a b u f f e r i n a Receive Message command, o r a b u f f e r w i l l
be t a k e n from a p o o l p r e v i o u s l y s u p p l i e d t o DDCMP.
I n some
i m p l e m e n t a t i o n s , i f DDCMP h a s n o t been i n i t i a l i z e d i n t o t h e
maintenance mode and a maintenance mode message is r e c e i v e d ,
t h e r e may be a s e p a r a t e r e s p o n s e i n d i c a t i n g t h a t t h e p r o t o c o l a t
t h e o t h e r end o f t h e l i n k is i n maintenance mode. A t t h a t p o i n t ,
t h e p r o t o c o l w i l l h a l t , and MOP w i l l have t o i n i t i a l i z e DDCMP
i n t o t h e maintenance mode pr i o r t o t r a n s m i t t i n g and r e c e i v i n g
maintenance messages.
I n t h e s e implementat i o n s , t h e o r i g i n a l
r e c e i v e d MOP message may be l o s t and n o t a c t u a l l y passed t o MOP.
MESSAGE R E C E I V E D IN ERROR
An o p t i o n a l r e p l y t o HOP i n d i c a t i n g t h a t a maintenance message
was r e c e i v e d w i t h a d a t a CRC ( b l o c k c h e c k ) e r r o r . DDCMP was a b l e
t o frame t h e message, b u t i t had one o r more b i t e r r o r s i n t h e
data field.
T h i s r e s p o n s e is u s e f u l i n r e d u c i n g t h e l e n g t h of
t i m e MOP w i l l w a i t f o r a r e p l y t o a p r e v i o u s l y s e n t message.
Without t h i s r e s p o n s e MOP w i l l w a i t f o r a MOP t i m e o u t i n t e r v a l .
The l e n g t h of t h i s i n t e r v a l is implementation s p e c i f i c , b u t must
i n c l u d e p r o c e s s i n g d e l a y s and t r a n s m i s s ion time. T y p i c a l l y , t h e
v a l u e would be t h e same a s t h e s e l e c t o r r e s p o n s e t i m e r v a l u e
used by t h e d a t a l i n k c o n t r o l p r o c e d u r e .
START RECEIVED

While i n maintenance mode, t h e remote s i d e s e n t a normal DDCMP
s t a r t message. When t h e l o c a l s i d e is p r o v i d i n g p a s s i v e loopback
s e r v i c e , t h i s o c c u r r e n c e n o t i f i e s i t t h a t t h e l i n e is t o be
r e s t a r t e d i n DDCMP normal mode.

4.0

MESSAGES

4.1

Message Format N o t a t i o n

A l l MOP messages a r e s e n t embedded

within a physical link control
protocol.
Within DECnet, t h e DDCMP maintenance mode e n v e l o p e is
g e n e r a l l y used f o r t h i s purpose. T h i s s e c t i o n p r e s e n t s t h e g e n e r a l
format of t h e MOP messages s e n t w i t h i n t h e d a t a f i e l d of t h a t
e n v e l o p e . Appendix B s p e c i f i e s t h e DDCMP Maintenance Mode f o r m a t .
The f o l l o w i n g n o t a t i o n is used t o d e s c r i b e t h e MOP messages:
FIELD (LENGTH):

D e s c r i p t i o n of f i e l d

CODING

Where:
FIELD

Is t h e name of t h e f i e l d being d e s c r i b e d .

LENGTH

Is t h e l e n g t h
following:
1.

the

field

expressed

one

the

The number of 8 - b i t b y t e s
The l e t t e r s "I-n" meaning image f i e l d w i t h n being a
number t h a t is t h e maximum l e n g t h i n & b i t b y t e s of
t h e image. The image is preceded by a 1 - b y t e c o u n t of
t h e l e n g t h of t h e remainder of t h e f i e l d .
Image
f i e l d s a r e v a r i a b l e l e n g t h and may be n u l l (count=O)
A l l 8 b i t s of each b y t e a r e used a s i n f o r m a t i o n b i t s .
I f t h e l e n g t h is " R a t h e f i e l d may e x t e n d t h e
remainder of t h e message (maximum l e n g t h is d e t e r m i n e d
from maximum message l e n g t h )

Is t h e r e p r e s e n t a t i o n t y p e u s e d , a s f o l l o w s :

CODING

B
BM

Null

Binary
B i t map ( e a c h b i t h a s independent meaning)
ASCII
I n t e r p r e t a t i o n depends on d a t a r e p r e s e n t a t i o n

Notes:
1.

A l l numeric v a l u e s a r e shown in d e c i m a l r e p r e s e n t a t i o n u n l e s s

otherwise noted.
f i e l d s a r e t r a n s m i t t e d low-order o r l e a s t - s i g n i f i c a n t b i t
f i r s t on t h e d a t a l i n k s u n l e s s o t h e r w i s e s p e c i f i e d .

A l l

B i t s i n a MOP f i e l d a r e numbered from 0 t o n where 0

the

low-order o r l e a s t - s i g n i f i c a n t b i t .
4.

Fields that refer
numbered a c c o r d i n g
system.

to
to

memory on s p e c i f i c
t h e c o n v e n t i o n s on

computers a r e
t h a t computer

The same names used i n f i e l d s i n s e p a r a t e messages
same meaning and f o r m a t .

have

the

4.2

MOP Message Formats

The g e n e r a l format of MOP messages is:

p+zq

Where:
CODE

Is t h e MOP message t y p e code (1 b y t e ) .

OPERAND

Is t h e operand i n f o r m a t i o n s p e c i f i c t o each message t y p e .

4.2.1

Memory Load w i t h T r a n s f e r Address

T h i s message c a u s e s t h e c o n t e n t s of t h e image d a t a t o be l o a d e d
( d e p o s i t e d ) i n t o memory a t t h e Load a d d r e s s and t h e system t o be
s t a r t e d a t ( t h e PC set t o ) t h e t r a n s f e r a d d r e s s .
I

CODE (1):B

LOADNUM ( 1) :B

I s t h e l o a d number f o r m u l t i p l e l o a d images.
This
message may be preceded by Memory Load w i t h o u t
T r a n s f e r Address messages. The l o a d number s t a r t s
a t z e r o and 1s incremented f o r each l o a d message
s e n t i n a l o a d i n g sequence. A l o a d number of z e r o
is always v a l i d and r e s e t s t h e e x p e c t e d l o a d number.
Zero s h o u l d n o t be used f o r a l l l o a d numbers i n a
sequence o f l o a d messages because i t n u l l i f i e s t h e
sequence c h e c k i n g o f t h e MOP p r o t o c o l .
LOADNUM
is
modulo 256. A f t e r l o a d number 255 is l o a d number 0 .

LOADADDR ( 4 ) : B

I s t h e memory l o a d a d d r e s s f o r s t o r a g e of
image.

IMAGE DATA

Is t h e image t o be s t o r e d i n t o computer memory. The
form s e n t w i l l be machine dependent and w i l l v a r y
w i t h t h e t y p e and word l e n g t h of t h e system:

Where :

VAX-11/780

the

data

Each b y t e
byte.

represents

memory

Each

represents

memory

byte

byte.
Each 3 b y t e s r e p r e s e n t s
words:

memory

Meaning
Low 8 b i t s of memory word 1 ( 4 - 1 1 )
Low 8 b i t s of memory word 2 ( 4 - 1 1 )
Low 4 b i t s of b y t e a r e h i g h
b i t s of1
word 1 (0-31, h i g h 4 - b i t s o f b y t e a r e 1
high 4 - b i t s of word 2 ( 0 - 3 ) .

DECSYSTEM 10/20
I

Each 5 b y t e s r e p r e s e n t s one 3 6 - b i t
word.
I

Meaning

Byte

1
2
3
4
5

I s the
loaded.

TRANSFER ADDR ( 4 ) :B

H i g h e s t numbered ( l o w - o r d e r ) 8 b i t s of
word (28-35)
Next 8 b i t s (20-27)
N e x t 8 b i t s (12-191
N e x t 8 b i t s (4-11)
Low 4 b i t s of b y t e a r e h i g h e s t o r d e r 4
b i t s o f word (0-3); h i g h e s t 4 b i t s of
b y t e a r e unused and set t o z e r o .
starting

address

the

image

just

NOTE
IMAGE DATA o r LOADADDR and IMAGE DATA
may be o m i t t e d .
V a l i d MOP message
l e n g t h s (DDCMP c o u n t v a l u e s ) w i l l be 6
(LOADADDR and IMAGE DATA o m i t t e d , 10
(IMAGE DATA o m i t t e d ) , o r g r e a t e r t h a n
10.

4.2.2

Memory Load w i t h o u t T r a n s f e r Address

T h i s message c a u s e s t h e c o n t e n t s of
t h e image
( d e p o s i t e d ) i n t o memory a t t h e l o a d a d d r e s s .
r

data

C O D E ] LOADNUM ; LOADADOR

IMAGE DATA

Where:
CODE (1):B

LOADNUM

I s described in Section 4 . 2 . 1 .

LOADADDR

I s d e s c r i b e d in S e c t i o n 4.2.1.

IMAGE DATA

I s d e s c r i b e d in S e c t i o n 4 . 2 . 1 .
NOTE
IMAGE DATA may be o m i t t e d .
V a l i d MOP
message l e n g t h s may be 6 (IMAGE DATA
o m i t t e d ) , or g r e a t e r t h a n 6 .
Messages
w i t h o u t IMAGE DATA c a u s e n o t h i n g t o be
l o a d e d , however, t h e LOADNUM v a l u e is
s t i l l incremented f o r ' t h e n e x t l o a d .

loaded

4.2.3

R e q u e s t Memory Dump

T h i s m e s s a g e r e q u e s t s a dump ( e x a m i n i n g ) o f a p o r t i o n o f memory t o
r e t u r n e d i n a memory d a t a dump m e s s a g e .
CODE

MEMADOR

NUMLOCS

Where:
CODE ( 1 ) : B

MEMADDR ( 4 ) :B

I s t h e s t a r t i n g memory a d d r e s s f o r t h e dump.

NUMLOCS ( 2 ) :B

I s t h e number o f l o c a t i o n s t o dump.
where:
POP-1 1
VAX-11/780
POP-8
DECSYSTEM-10/20

1 location
1 location
1 location
1 location

is 1 b y t e .
is 1 b y t e .
is 1 word.
is 1 word.

NOTE
T h i s r e q u e s t r e s u l t s i n a s i n g l e Memory
Dump D a t a m e s s a g e . A dump s h o u l d n o t b e
r e u u e s t e d f o r more d a t a t h a n c a n b e
r e l i a b l y s e n t i n a s i n g l e reply on t h e
l i n k t y p e used.
The
maximum
link
c o n t r o l p r o c e d u r e m e s s a g e l e n g t h limits
t h e maximum l e n g t h f o r a g i v e n l i n k .

4.2.4

E n t e r MOP Mode

T h i s m e s s a g e c a u s e s a s y s t e m n o t i n t h e MOP mode t o e n t e r t h e MOP mode
i f t h e p a s s w o r d m a t c h e s . T h i s u s u a l l y means t r a n s f e r r i n g c o n t r o l on
t h e s a t e l l i t e t o a MOP p r o g r a m .

Where:

PASSWORD ( 4 ) : B

I s a password t h a t must match b e f o r e t h e r e c e i v i n g
s t a t i o n c a n e n t e r t h e MOP mode. I f t h e p a s s w o r d is
s e n t o v e r a DDCMP l i n k i n t h e m a i n t e n a n c e mode, t h e
l i n k w i l l e n t e r t h e DDCMP m a i n t e n a n c e mode ( d u e t o
t h e m a i n t e n a n c e mode e n v e l o p e ) , b u t t h e node w i l l
o n l y e n t e r t h e MOP mode ( f o r e x a m p l e , r e s p o n d t o l o a d
r e q u e s t s ) i f t h e PASSWORD m a t c h e s .

Request Program

4.2.5

This message requests a program to be sent in some
load messages.
CODE

MOPVER

DEVTYPE

PGMTYPE

number

memory

SOFTID

Where:
CODE (I): B
I s the device type at the requesting system.
Used
to cause the proper requested program to be loaded
if it is device specific. Device types include:

DEVTYPE (1): B

Value

Meaning
DP
DU
DL

(DP-DA SYNCHRONOUS LINE INTERFACE)
(DU-DA SYNCHRONOUS LINE INTERFACE)
(DL-C AND -E ASYNCHRONOUS SERIAL LINE
INTERFACE)
DQ (DQ-DA SYNCHRONOUS SERIAL LINE INTERFACE)
D A (DA-B O R -AL UNIBUS LINKS)
DUP (DUP-DA SYNCHRONOUS LINE INTERFACE)
OMC (DMC-DA/AR, -MA/AL, -FA/AR INTERPROCESSOR
LINKS 1
ON (ON-BA O R -AA AUTOMATIC CALLING UNIT)
DLV (DLV-E ASYNCHRONOUS LINE INTERFACE)
DMP
DTE
DV (DV-AA/BA SYNCHRONOUS LINE MULTIPLEXER)
0 2 (02-A O R -8 ASYNCHRONOUS SERIAL LINE
INTERFACE)
KDP (KMC/DUP-DA SYNCHRONOUS LINE MULTIPLEXER)
KDZ (KMC/DZ-A ASYNCHRONOUS LINE MULTIPLEXER)
KL (KL8J

MOPVER

( 1) :B

Is
the
MOP
specifications
number is 1.

PGMTYPE ( 1 ):B

format
version

version
number.
For
and 2 the format version

I s the generic type of program requested.
Appendix
C describes these types. T h e program type numbers
are as follows:

Value

Meaninq

0 (or omitted)

Secondary loader
Tertiary loader
Operating system

1
2

SOFTID (I-R) : A

Identifies the software being requested.
Specified
as
an imaqe field of ASCII characters.
This
information is not needed if PGMTYPE is enough to
specify the requested program.
Also omitted if
PGMTYPE is omitted.

Request Memory Load

4.2.6

T h i s message r e q u e s t s t h e n e x t l o a d i n a l o a d i n g sequence and p r o v i d e s
e r r o r s t a t u s on t h e p r e v i o u s l o a d .
CODE

ERROR

LOADNUM

Where:
CODE ( 1 ) : B

LOADNUM ( 1 ) : B

I s t h e number of t h e l o a d being r e q u e s t e d .

ERROR (1): B

Is the e r r o r indicator
segment, a s f o l l o w s :

for

Value
- -

load

numbered

Meaning

0 ( o r omitted)

No e r r o r .
Memory Load message image d a t a n o t
properly
loaded
( f o r example,
because of a
memory
boundary
problem).

MOP Mode Running

4.2.7

T h i s message i n d i c a t e s t o a h o s t t h a t t h e system is i n
and s u p p o r t s t h e f e a t u r e s i n d i c a t e d .
CODE

MOPVER

DEVTYPE

MEMSIZE

the

MOP

mode

FEATURES

Where:
CODE (1):B

DEVTYPE

Is d e s c r i b e d i n S e c t i o n 4 . 2 . 5 .

MOPVER

Is d e s c r i b e d i n S e c t i o n 4 . 2 . 5 .

MEMSIZE ( 4 ) :B

I s t h e s i z e of p h y s i c a l machine memory i n number of
contains the location
locations.
Section 4.2.3
definition.

FEATURES (1):BH

Features a v a i l a b l e a t t h i s s t a t i o n according t o

the

b i t ( s ) set.

it 1

Feature
Multiblock
messages:

load.

Accepts

the

following

1. Memory Load With T r a n s f e r Address message
Load Without
Transfer
Address
messaqe
3 . Parameter Load W i t h
Transfer
Address
message

2 . Memory

Dump.
Accepts
message.
2

Loopback.

3-7

Reserved.

the

Request

Memory

Dump

Accepts t h e Loopback T e s t message.

4.2.8

Memory D u m p Data

T h e Memory Dump Data message, replying to a
message, sends back the requested memory image.
CODE

MEMADDR

Request

Memory

Dump

DATA

IMAGE DATA

Where:
CODE ( 1 ):B

MEMADDR (4):B

I s the starting address o f t h e dump.

IMAGE DATA

Is the dump o f memory in the same form as IMAGE
in Section 4.2.1.

4.2.9

Reserved for Remote-11 Use

Remote-11, a networking product using RT-11 uses this message type.

[GqZGq
J

Where:
CODE (1):B

MESSAGE

Refer to Remote-11 documentation.

4.2.10

Reserved for Remote-11 U s e

Remote-11, a networking product using RT-11 uses this message type.

'1 CODE 1 MESSAGE 1
Where:
CODE ( 1 ):B

MESSAGE

Refer to Remote-11 documentat ion.

4.2.11

Parameter Load with Transfer Address

T h i s message is used instead of Memory Load with Transfer Address
(as
the last load) to load system parameters before transferring control
to the loaded program.

7
I CODE ' Lo A m u M 1 PARAMETERS i TRANSFER ADDR 1
1

Where:
CODE (1):B

LOADNUM

Refer to Section 4.2.1.-

PARAMETERS

ENTRY,
ENTRY

ENTRY,

. . . ,ENDMARK
PARTYPE,
PARLENGTH,
PARVALUE
E N T R Y f i'elds a r e optional)

E (1):B

Parameter t y p e number

PARLENGTH (1): B

Number o f b y t e s i n PARVALUE

PARVALUE

Parameter
value
according
to
PARTYPE and PARLENGTH, a s f o l l o w s :

PARTYPE

PARLENGTH

PARVALUE

1 to 6

ASCII node name t a r g e t node is
t o use f o r i t s e l f .

1 to 2

B i n a r y node number t a r g e t node
is t o use f o r i t s e l f .

1 to 6

ASCII name of h o s t a s s i g n e d t o
node
( f o r example, c o n t r o l
host for task
loading
of
core-only systems).

1 to 2

B i n a r y node number
a s s i g n e d t o node.

ENDMARK ( 1) :B

TRANSFER ADDR

Refer t o S e c t i o n 4.2.1

host

NOTE
The parameter message,
i f used,
is t h e l a s t i n a
m u l t i b l o c k l o a d . The minimum MOP message l e n g t h is 7 .
The f o l l o w i n g t e c h n i q u e s p a s s t h e p a r a m e t e r s t o t h e
o p e r a t i n g systems:
POP-8

Currently unspecified.

POP-11

S t o r e t h e parameters a t t h e top of physical
memory i n t h e l o c a t i o n s l i s t e d below.
"Top of memory" r e f e r s t o t h e f i r s t even
a d d r e s s beyond a v a i l a b l e memory.
I t s value
is t h e same a s t h e v a l u e r e t u r n e d i n t h e
MEMSIZE f i e l d ( S e c t i o n 4 . 2 . 7 ) .

Top of memory - 6 2 .
bytes =
a 6-byte node name padded w i t h s p a c e s .

Top of memory
64.
bytes =
a 2-byte node number.
I f none, t h e n z e r o s .
If

none, t h e n f i r s t 2 b y t e s a r e z e r o s .

56.
bytes =
Top of memory
a 6-byte h o s t node name padded w i t h s p a c e s .
I f none, t h e n f i r s t 2 b y t e s a r e z e r o s .

Top o f memory
50.
bytes =
a l l b y t e s through t o p of memory r e s e r v e d

The r e g i s t e r s a r e s e t a s f o l l o w s :
RO
Rl

R2
R3
R4

Load d e v i c e CSR a d d r e s s
-1
-1
U n i t number o f l o a d d e v i c e
2 - b y t e ASCII l o a d d e v i c e

mnemon i c :

4.2.12

VAX-11/780

Currently unspecified.

DECSYSTEM-10/20

Currently unspecified.

Loopback T e s t

The Loopback T e s t m e s s a g e t e s t s a l i n k by e c h o i n g t h e m e s s a g e s e n t .
The a c t i v e s i d e s e n d s t h e m e s s a g e ;
the passive s i d e echoes t h e
messaqe.
Upon r e c e i v i n g t h e e c h o e d m e s s a g e , t h e o r i g i n a l s e n d e r d o e s
( T h a t would c a u s e a n i n f i n i t e l o o p . ) I f t h e
not echo it again.
p a s s i v e s i d e is a c o m p u t e r , i t c h a n g e s t h e f u n c t i o n c o d e t o Looped
Data b e f o r e e c h o i n g t h e message. T h i s p r e v e n t s a n i n f i n i t e l o o p where
t h e a c t i v e s i d e a b o r t s t h e t e s t , r e c e i v e s a n e c h o e d Loopback T e s t
m e s s a g e from a p a s s i v e c o m p u t e r , a n d e c h o e s t h e m e s s a g e .
I f the
p a s s i v e s i d e is u n i n t e l l i g e n t , i t e c h o e s t h e Loopback T e s t Message
unchanged.
In t h i s case, the aborted active side eventually receives
a Looped D a t a Message and t e r m i n a t e s t h e p a s s i v e l o o p b a c k .

Where:
CODE (1): B

LOOP DATA

Is t h e d a t a t o be looped back.
T h i s m e s s a g e is
returned exactly a s sent.
The maximum l e n g t h is
l i m i t e d b y the maximum l i n k c o n t r o l p r o c e d u r e m e s s a g e
length for a given link.

4.2.13

Looped D a t a

The Looped D a t a m e s s a q e is r e t u r n e d by a n i n t e l l i g e n t
i n r e s p o n s e t o a Loopback T e s t message.
CODE

passive

looper

LOOPDATA

Where:
CODE ( 1 ) : B

LOOPDATA

I s the d a t a received

i n t h e Loopback T e s t message.

5.0

OPERATION

MOP messages a r e s e n t w i t h i n a l i n k c o n t r o l

procedure t h a t provides
t h e f u n c t i o n s of message framing and b i t e r r o r d e t e c t i o n . MOP
o p e r a t e s between two computer s y s t e m s d i r e c t l y connected by a d a t a
l i n k , which is d e d i c a t e d t o t h e MOP o p e r a t i o n . On m u l t i p o i n t l i n k s ,
t h e s u b c h a n n e l c o n n e c t i n g t h e two s y s t e m s is d e d i c a t e d t o MOP
operation.
MOP messages a r e s e n t a l t e r n a t e l y between t h e c o m p u t e r s .
One system is d e s i g n a t e d t h e h o s t and t h e o t h e r , t h e s a t e l l i t e .
The
h o s t c o n t r o l s MOP o p e r a t i o n and u s u a l l y i n i t i a t e s t h e e r r o r r e c o v e r y
p r o c e d u r e s . The h o s t p r o v i d e s t h e d a t a f o r t h e memory l o a d , r e c e i v e s
t h e d a t a from t h e memory dump, and p e r f o r m s t h e l i n k t e s t f u n c t i o n .
The s a t e l l i t e is t h e o b j e c t o f t h e l o a d , r e s p o n d s w i t h d a t a f o r t h e
dump, and e c h o e s messages f o r t h e l i n k t e s t i n g f u n c t i o n . A l l message
acknowledgment, t i m e o u t , and r e t r a n s m i s s i o n f u n c t i o n s a r e handled a t
t h e MOP l e v e l v i a MOP messages and f u n c t i o n s . The l i n k c o n t r o l
p r o c e d u r e o n l y p r o v i d e s a b i t e r r o r check. S e c t i o n 3 d e s c r i b e s t h e
l i n k c o n t r o l procedure functions.
The DNA-defined l i n k c o n t r o l p r o c e d u r e is t h e DDCMP maintenance mode.
The DDCMP F.u n---.-.
c t i o n a l.---------S p e c i f i c a t i o n c o n t a i n s a complete d e s c r i p t i o n of
DDCMP.
I t is p o s s i b l e t o add t o MOP t h e c a p a b i l i t y of o b t a i n i n g

load images
from and of s t o r i n g dump images a t o t h e r nodes r a t h e r t h a n u s i n g l o c a l
host storage.
Thus remote nodes n o t d i r e c t l y c o n n e c t e d t o t h e
s a t e l l i t e can c o n t r o l l o a d i n g and dumping f u n c t i o n s . R e g a r d l e s s of
where t h e h o s t g e t s o r s e n d s t h e s a t e l l i t e d a t a , t h e o p e r a t i o n between
t h e h o s t and s a t e l l i t e is t h e same.
In g e n e r a l , the l i n k c o n t r o l procedure should buffer
incoming
messaqes, check them f o r b i t e r r o r s , and t h e n p a s s them t o MOP. The
b u f f e r a r e a s h o u l d be chosen s o t h a t i t d o e s n o t c o n f l i c t w i t h a r e a s
o f memory r e q u i r i n g MOP a c c e s s ( f o r example, l o a d i n g o r dumping).
Load images s h o u l d n o t be loaded d i r e c t l y i n t o t h e s p e c i f i e d l o a d
a d d r e s s i n l o a d messaqes. Messages w i t h b i t e r r o r s might have l o a d
a d d r e s s e s i n e r r o r , which would c a u s e them t o be loaded i n t o t h e wrong
a r e a of memory, p o s s i b l y d e s t r o y i n g i m p o r t a n t i n f o r m a t i o n . The o n l y
e x c e p t i o n t o t h i s r e s t r i c t i o n is t h e l o a d i n g of t h e s e c o n d a r y l o a d e r ,
which is known i n advance ( b y s p e c i f i c a t i o n ) t o be loaded i n a
p a r t i c u l a r memory a r e a .
MOP u s e s t i m e o u t s t o r e c o v e r from e r r o r s .

That i s , when a command is
s e n t , a t i m e r is s t a r t e d .
I f a r e s p o n s e is not r e c e i v e d w i t h i n a
timeout i n t e r v a l , t h e timer e x p i r e s and e r r o r r e c o v e r y p r o c e d u r e s a r e
i n i t i a t e d . The h o s t system u s u a l l y h a n d l e s t h e timeout f u n c t i o n . The
e x c e p t i o n t o t h i s is MOP primary mode i n i t i a l i z a t i o n where t h e
s a t e l l i t e ' i s i n t h e MOP mode and t h e h o s t is n o t . In t h i s c a s e ,
t i m e o u t s and r e t r a n s m i s s i o n occur from t h e s a t e l l i t e .
The l i n k
c o n t r o l p r o c e d u r e p a s s e s messages w i t h o u t b i t e r r o r s t o MOP and
i g n o r e s a l l o t h e r s . MOP'S t i m e o u t mechanism r e c o v e r s t h e messages
that
the
link
c o n t r o l p r o c e d u r e ignored due t o b i t e r r o r s .
O p t i o n a l l y , t h e l i n k c o n t r o l p r o c e d u r e may n o t i f y MOP t h a t a message
was r e c e i v e d w i t h one o r more b i t e r r o r s . I n t h i s c a s e , MOP may
i n i t i a t e e r r o r r e c o v e r y p r o c e d u r e s p r i o r t o t h e e x p i r a t i o n of t h e
T h i s may improve t h e performance of MOP on l i n k s
response timeout.
w i t h high e r r o r r a t e s .
T h e e r r o r recovery procedures
a r e t h e same,
whether i n i t i a t e d i n r e s p o n s e t o a t i m e o u t o r n o t i f i c a t i o n from t h e
l i n k c o n t r o l p r o c e d u r e of message r e c e p t i o n w i t h b i t e r r o r s .

5.1

MOP Primary and Secondary Mode O p e r a t i o n

Program l o a d i n g , image dumping, and l i n k t e s t i n g u s u a l l y occur i n MOP
secondary mode.
I f t h e r e is enough s p a c e w i t h i n t h e s a t e l l i t e t o
c o n t a i n t h e e n t i r e secondary program ( e i t h e r w i t h i n ROM, o r loaded
from a l o c a l load d e v i c e ) , t h e s a t e l l i t e s t a r t s i n t h e MOP s e c o n d a r y
mode. O t h e r w i s e , a minimum program, primary mode, b o o t s t r a p s t h e
s a t e l l i t e system t o t h e s e c o n d a r y mode. The o p e r a t i o n t o a c h i e v e
secondary mode is:

I f t h e primary program is r u n n i n g , i t s e n d s a Request Program
message t o t h e h o s t system r e q u e s t i n g t h e s e c o n d a r y l o a d e r .

When t h e h o s t r e c e i v e s t h i s message, i t s e n d s t h e e n t i r e
s e c o n d a r y program i n t h e form o f a s i n g l e Memory Load w i t h
T r a n s f e r Address message.

I f t h i s is i n e r r o r ( n o message r e c e i v e d ) , t h e primary
program s e n d s a n o t h e r Request Program message a f t e r a t i m e o u t
per iod.

Once t h e secondary l o a d e r is loaded and r u n n i n g ,
secondary l o a d e r may send one of t h e f o l l o w i n g :

the

The Request Program message t o r e q u e s t a s p e c i a l f u n c t i o n
program ( f o r example, t e r t i a r y l o a d e r ) o r an o p e r a t i n g
system

The MOP Mode Running message t o t e l l t h e h o s t what
f u n c t i o n s a r e a v a i l a b l e and w a i t f o r t h e h o s t t o i n i t i a t e
a c t ion

The c h o i c e of message depends on t h e c a p a b i l i t i e s of t h e s p e c i f i c
secondary proqram t h a t was loaded.
I f i t is an advanced l o a d e r
program o n l y ( f o r example, t e r t i a r y l o a d e r ) t h e n t h e h o s t s e n d s a
Request
Program
message.
If
t h e loaded program L S a more
g e n e r a l - p u r p o s e secondary program c a p a b l e of m u l t i p l e f u n c t i o n s ( f o r
example, l o a d , dump, t e s t ) , t h e n t h e h o s t s e n d s t h e MOP Mode Running
message. T h i s f l e x i b i l i t y a l l o w s c o n t r o l r e q u e s t s t o come from e i t h e r
t h e s a t e l l i t e o r t h e h o s t depending on t h e o p e r a t i n g r e q u i r e m e n t s .
I f t h e secondary l o a d e r a l r e a d y e x i s t s in t h e s a t e l l i t e s y s t e m , t h e
d i a l o g u e s t a r t s a t S t e p 4 above.
The a c t i o n taken in S t e p 4
d e t e r m i n e s whether ( 1 ) t h e s a t e l l i t e wants t o i n i t i a t e a c t i o n ( f o r
example, load memory) or ( 2 ) t h e h o s t s e l e c t s t h e MOP f u n c t i o n ( t h e
S a t e l l i t e t e l l s t h e h o s t t h a t t h e MOP mode is r u n n i n g ) .
There may be many secondary l o a d e r s w i t h d i f f e r e n t c a p a b i l i t i e s .
The
s p e c i f i c network and h o s t d e t e r m i n e which is t h e a p p r o p r i a t e one t o
u s e . Once t h e secondary l o a d e r is l o a d e d , i t may load o t h e r l o a d e r s
using t h e l o a d i n g memory f u n c t i o n .
Each DECnet i r n p l e m e n t a t ~ o n r e a u i r e s a s y s t e m - s p e c i f i c primary program.
However, a l l primary programs must exchange t h e same p r o t o c o l messages
a c c o r d i n g t o t h e same r u l e s , even though t h e programs a r e d i f f e r e n t
internally.
The r e q u i r e d o p e r a t i o n of t h e primary proqram f o r e a c h
computer f a m i l y is a s f o l l o w s :
POP-8.

Currently unspecified

The primary program s e n d s a Request Program message f o r
t h e secondary l o a d e r (PGMTYPE and SOFTID i n message a r e o m i t t e d ) .
I t e x p e c t s t h e secondary l o a d e r t o be r e t u r n e d i n a s i n g l e Memory
Load w i t h T r a n s f e r Address message. I n t h i s message, t h e f i e l d s
must have t h e f o l l o w i n g v a l u e s :

PDP-11.

LOADNUM
LOADADDR

" 0
6
TRANSFER ADDR
6

The MOP message (from CODE t o TRANSFER ADDR)
is loaded a t
l o c a t i o n 0 . T h a t i s , t h e secondary l o a d e r (IMAGE DATA f i e l d ) is
loaded i n a s i n g l e message b l o c k , s t a r t i n g a t l o c a t i o n 6 in
p h y s i c a l memory w i t h a s t a r t i n g t r a n s f e r a d d r e s s t o l o c a t i o n 6 .
Upon t r a n s f e r , t h e PDP-11 r e g i s t e r s have t h e f o l l o w i n g v a l u e s :
Rl

load d e v i c e CSR a d d r e s s

The primary l o a d e r s t a r t s a t i m e r w h i l e w a i t i n g f o r t h e Memory
Load message.
I f t h e secondary l o a d e r is r e c e i v e d i n e r r o r , i f
no l o a d e r is r e c e i v e d o r i f any o t h e r message is r e c e i v e d , t h e
primary program t i m e s o u t and r e s t a r t s , r e t r a n s m i t t i n g t h e
Request Program message a g a i n .
I f t h i s c y c l e o c c u r s some
t h r e s h o l d number of t i m e s , t h e s a t e l l i t e assumes t h e h o s t is n o t
answering and may d i s c o n n e c t t h e Link ( f o r example, "hang up" a
switched c i r c u i t ) .
VAX-11/780.

Currently unspecified

DECsystem-10/20.

5.2

Currently unspecified

Loading Computer Memory

Memory l o a d i n g o c c u r s i n t h e MOP secondary mode. E i t h e r t h e s a t e l l i t e
secondary program o r t h e h o s t may i n i t i a t e l o a d i n g a s d e s c r i b e d i n
S t e p 4 of S e c t i o n 5.1.
I n e i t h e r c a s e , l o a d i n g o c c u r s by t h e exchange
of Memory Load messages from t h e h o s t and Request Memory Load
r e s p o n s e s from t h e s a t e l l i t e . Loading s t a r t s w i t h load number 0 and
is incremented f o r each s u c c e s s i v e l o a d . The h o s t s e n d s a Memory Load
w i t h a load number of 0 . I f t h e Memory Load message has no b i t
e r r o r s , i t is loaded i n t o memory, and a Request Memory Load f o r load
number 1 is r e t u r n e d by t h e s a t e l l i t e . T h i s both acknowledges load 0
and r e q u e s t s t h e n e x t load ( l o a d 1 ) . Any e r r o r o c c u r r i n g a t t h e
s a t e l l i t e in load 0 is r e p o r t e d i n t h i s message a s w e l l .
I f t h e load message is i n e r r o r , t h e s a t e l l i t e d o e s n o t h i n g and w a i t s
f o r t h e h o s t t o t i m e o u t and r e t r a n s m i t t h e l o a d . I f t h e wrong load
number is r e c e i v e d , t h e s a t e l l i t e responds w i t h a r e q u e s t f o r t h e
expected load number. A l t e r n a t e l y , i f t h e s a t e l l i t e is confused ( f o r
example, wronq load r e c e i v e d t o o many t i m e s ) i t may go back t o i t s
i n i t i a l s t a t e and send e i t h e r a MOP Mode Running message o r a Request
Program message back t o t h e h o s t . The h o s t is t h e n r e s p o n s i b l e f o r
I n g e n e r a l , t h e h o s t is
r e s t a r t i n g t h e load from load 0 a g a i n .
c a p a b l e of more i n t e l l i g e n c e than t h e s a t e l l i t e , and t h u s t h e h o s t has
burden of t h e e r r o r recovery.
I f t h e h o s t r e c e i v e s a message w i t h b i t
e r r o r s , i t should send i t s l a s t message a g a i n , e i t h e r upon a t i m e o u t
Or o p t i o n a l l y , on n o t i f i c a t i o n of t h e e r r o r from t h e l i n k c o n t r o l
procedure.
The f i n a l load c a u s e s t h e secondary mode l o a d e r t o t r a n s f e r t o t h e
d e s i q n a t e d t r a n s f e r a d d r e s s a f t e r , o p t i o n a l l y , acknowledging t h a t l a s t
Load w i t h a Request Memory Load message f o r t h e n e x t exoected load

( t h e l o a d a f t e r t h e l a s t o n e ) . The acknowledgment is o m i t t e d when i t
is known t h a t t h e loaded program w i l l i t s e l f be sending MOP messages
a s i n t h e c a s e of t h e l o a d i n g of a h i g h e r l e v e l MOP f u n c t i o n . I f t h e
program r e q u e s t e d was a l o a d e r , t h e f i n a l l o a d is acknowledged, s i n c e
the
loader
sends
a Request Program message when i t s t a r t s ,
acknowledging i t s proper o p e r a t i o n . The f i n a l l o a d , i n c l u d i n g t h e
t r a n s f e r a d d r e s s , may be e i t h e r a Program Load w i t h T r a n s f e r Address
message o r a Parameter Load w i t h T r a n s f e r Address message.
I f t h e h o s t r e c e i v e s a MOP Mode Running o r Request Program message
f o l l o w i n g t h e s e n d i n g o f t h e message w i t h a t r a n s f e r a d d r e s s , t h e
r e c e i v e d message s h o u l d be examined t o d e t e r m i n e i f i t was s e n t by t h e
program t o which t h e h o s t i n t e n d e d t o t r a n s f e r c o n t r o l o r was s e n t by
t h e MOP l o a d e r t o which t h e t r a n s f e r message was s e n t .
This
d e t e r m i n a t i o n d i s t i n g u i s h e s between t h e i n i t i a l l o a d r e q u e s t o f a new
l o a d e r and t h e r e s t a r t i n g of t h e c u r r e n t l o a d e r .
This determination
i n v o l v e s comparing t h e program r e q u e s t o r f e a t u r e s f i e l d s of t h e
r e c e i v e d message a g a i n s t t h e c u r r e n t l o a d i n g p a r a m e t e r s t o d e t e r m i n e
i f t h e y came from t h e o l d o r new program.
I f t h e y came from t h e o l d
program, t h e n l o a d i n g s h o u l d s t a r t a g a i n from t h e b e g i n n i n g . I f t h e y
came from t h e new program, t h e n s u c c e s s f u l l o a d i n g h a s o c c u r r e d and
new MOP o p e r a t i o n may commence.
Loads t h a t exceed memory limits a r e n o t Loaded and c a u s e t h e n e x t l o a d
t o be r e q u e s t e d w i t h an e r r o r code ( E R R O R f i e l d ) i n c l u d e d i n t h a t
r e q u e s t . I n some c a s e s , t h e s e c o n d a r y l o a d e r r e q u e s t s an advanced
l o a d e r ( a t e r t i a r y l o a d e r ) , which t h e n l o a d s t h e o p e r a t i n g system.
One MOP program may load a n o t h e r v i a t h e l o a d memory p r o c e d u r e s and
t h u s t r a n s f e r from one MOP program t o a n o t h e r i n a s e r i e s of MOP
operations.

5.3

Dumping Computer Memory

The h o s t system i n i t i a t e s t h e dumping f u n c t i o n by sending Request
Memory Dump messages t o t h e s a t e l l i t e system. The s a t e l l i t e t h e n
responds w i t h a Memory Dump Data message.
I f no r e p l y is r e t u r n e d ,
t h e h o s t t i m e s o u t and r e p e a t s t h e r e q u e s t .
I Â the s a t e l l i t e receives
a message w i t h b i t e r r o r s , i t may respond i n one of two ways:
1.

I g n o r e them and l e t t h e h o s t time o u t .

Return a MOP ode Runninq message t o c a u s e r e t r a n s m i s s i o n
t h e r e q u e s t a t t h e h o s t p r i o r t o timer e x p i r a t i o n .

Requests o u t s i d e memory bounds r e s u l t i n t r a n s m i s s i o n of a Memory Dump
Data message w i t h z e r o s f o r image d a t a . Requests f o r more t h a n can be
s e n t i n a s i n g l e block r e s u l t in t r a n s m i s s i o n o f t h e maximum t h a t can
be s e n t i n a block. The remainder of t h e r e q u e s t is i g n o r e d .

5.4

Link T e s t i n g

The Loopback T e s t message t e s t s t h e c o n d i t i o n o f a d a t a l i n k .
The
message i s s e n t by t h e h o s t , t u r n e d a r o u n d , and r e t u r n e d on t h e d a t a
link.
T h e a c t u a l looping back may be done by a program i n t h e
s a t e l l i t e o r by a loopback box o r s w i t c h p l a c e d somewhere between t h e
h o s t and s a t e l l i t e systems. W i t h t h i s t e c h n i q u e , problems can be
p i n p o i n t e d b y moving t h e loopback p o i n t and i s o l a t i n g components.

5.5

Unattended C o n t r o l

The E n t e r MOP Mode message c o n t r o l s u n a t t e n d e d s y s t e m s . I f s e n t t o a
it causes the
running
s a t e l l i t e t h a t implements t h i s message,
s a t e l l i t e t o t r a n s f e r c o n t r o l t o MOP p r i m a r y o r s e c o n d a r y mode
programs i n t h e s a t e l l i t e . I f implemented i n hardware, t h e hardware
s e a r c h e s f o r t h e p r o p e r E n t e r MOP Mode message s t r i n g . Upon a match,
t h e hardware c a u s e s a t r a n s f e r t o t h e MOP program, u s u a l l y r e s i d i n g i n
r e a d o n l y memories. T h i s a l l o w s a system t h a t is i n a l o o p o r t h a t i s
h a l t e d t o be remotely c o n t r o l l e d and r e b o o t e d .
A password, p a r t of t h e E n t e r MOP Mode

message, a v o i d s improper o r
a c c i d e n t a l u s e . Only a message w i t h a matching password is c o n s i d e r e d
v a l i d and p r o c e s s e d . A l l o t h e r s a r e i g n o r e d . Upon e n t e r i n g MOP mode,
t h e p r i m a r y o r s e c o n d a r y program e x e c u t e s a s d e s c r i b e d i n S e c t i o n 5 . 1 .

6.0

MOP STATES, EVENTS, AND ACTIONS

T h i s s e c t i o n p r e s e n t s t h e p o s s i b l e s t a t e s , e v e n t s , and a c t i o n s of h o s t
In general, events
and s a t e l l i t e systems running t h e MOP p r o t o c o l .
a r e r e c e p t i o n s of MOP messages fro,m t h e o t h e r system o r t i m e o u t s .
A c t i o n s a r e s t e p s t o be t a k e n upon t h e o c c u r r e n c e o f an e v e n t . The
p a r t i c u l a r a c t i o n t o be t a k e n depends on t h e s t a t e of t h e h o s t or
s a t e l l i t e . The t a b l e s i n t h i s s e c t i o n s p e c i f y t h e s e r e l a t i o n s h i p s .
The p o s s i b l e s a t e l l i t e s t a t e s a r e a s f o l l o w s :

non-MOP

The s a t e l l i t e is n o t i n MOP mode.

PRIMARY MODE

The s a t e l l i t e is running t h e b a s i c primary
mode program and t r y ing t o l o a d t h e s e c o n d a r y
program from t h e Host.

SECONDARY MODE

The s a t e l l i t e is running t h e s e c o n d a r y mode
program and w a i t i n g f o r a command from t h e
Host.

LOADING MODE

The s a t e l l i t e is running i n t h e s e c o n d a r y
l o a d i n g mode where i t is r e q u e s t i n g l o a d s
from t h e h o s t and l o a d i n g them i n t o memory.

The s a t e l l i t e performs t h e f o l l o w i n g a c t i o n s , c l a s s i f i e d a c c o r d i n g t o
state.
The numbers p r e c e d i n g each a c t i o n a r e used f o r r e f e r e n c e i n
t h e s a t e l l i t e s t a t e t a b l e ( T a b l e 1) t h a t f o l l o w s t h i s l i s t of a c t i o n s .
1.1 I f primary code is a v a i l a b l e i n t h e s a t e l l i t e , t h e n send Request
Program message f o r secondary code and e n t e r Primary s t a t e . I f
secondary code is a v a i l a b l e , t h e n send one of t h e f o l l o w i n g :
( a ) The Request Program message f o r a t e r t i a r y l o a d e r o r o p e r a t i n g
system ( i f secondary is o n l y a l o a d e r ) and e n t e r Loader S t a t e .
( b ) The MOP Mode Running message ( i f
s u p p o r t e d ) and e n t e r secondary s t a t e .

other

functions

are

2.1 V a l i d Memory Load i s per r e q u i r e m e n t s of primary code f o r each
computer f a m i l y .
I f loaded then t a k e a c t i o n a s f o r s e c o n d a r y code
under 1. l .
2.2 Send Request Program message a g a i n and w a i t foc secondary c o d e .
2.3 Take a c t i o n a s i n 2 . 2
u n t i l some t h r e s h o l d i s
r e s e t , hanging up l i n k i f a d i a l - t y p e c o n n e c t i o n .

exceeded,

3 . 1 I f load number 0 , t h e n h a n d l e a s if message had been
Loading s t a t e .

then

received

3 . 2 Send Memory Dump Data r e s p o n s e .
3 . 3 Change f u n c t i o n code t o Looped Data and echo message.
3 . 4 E i t h e r i g n o r e o r send messages a s d e s c r i b e d

for

secondary

under

1.1.
4 . 1 V a l i d Memory Load per r e q u i r e m e n t s

of computer f a m i l y , LOADNUM
f i e l d must be a s expected
( o r z e r o ) . I f v a l i d t h e n load i n t o
memory, send a Request Memory Load f o r r e c e i v e d LOADNUM + 1 .

4 . 2 E i t h e r send Request Memory Load f o r e x p e c t e d LOADNUM o r i g n o r e .
4.3

I f Memory Load w i t h T r a n s f e r , f i r s t l o a d memory p a r t .
If
Parameter Load w i t h T r a n s f e r , s e t up parameter l i s t . I f t h e
t r a n s f e r is t o an o p e r a t i n g system ( o r o t h e r non-MOP p r o g r a m ) ,
send Request Memory Load f o r LOADNUM + 1 and t h e n t r a n s f e r t o
TRANSFER ADDR.

4.4

E i t h e r send Request Memory Load f o r e x p e c t e d LOADNUM o r r e t u r n t o
Secondary s t a t e and t a k e a c t i o n a s under 1.1 f o r secondary code.
Table 1
S a t e l l i t e S t a t e Table
State

Event

New S t a t e

non-MOP

Receive v a l i d
E n t e r MOP Mode

Primary,
Secondary, o r
Lo ad i nq

User r e q u e s t s
MOP mode

Pr imary o r
Secondary

Receive v a l i d
Memory l o a d
with Transfer
address

Secondary o r
Load ing

Receive o t h e r
message

Pr imary

T imeou t

Pr imary

Receive Memory
Load

Receive T r a n s f e r

Non-Mop

Receive Dump
request

Secondary

Receive Loopback
T e s t Message

Secondary

Receive other

Secondary

Primary

Secondary

messaqe
Load inq

Receive v a l id
Memory Load

Receive i n v a l i d
Memo r y Lo ad

Load inq

Receive T r a n s f e r

non-MOP

Receive o t h e r
messaqe

Loading o r
Secondary

Act ion

The h o s t s t a t e s a r e a s f o l l o w s :
non-MOP

The h o s t is n o t i n MOP mode w i t h
t h e connected s a t e l l i t e .

respect

LOADING MODE

The h o s t i s
satellite.

the

memory

the

DUMPING MODE

The h o s t
satellite.

dumping

the

memory

the

L I N K TEST MODE

The h o s t is t e s t i n g t h e d a t a l i n k .

The h o s t performs t h e f o l l o w i n g a c t i o n s , c l a s s i f i e d a c c o r d i n g t o
state.
The numbers p r e c e d i n g t h e a c t i o n s a r e used f o r r e f e r e n c e i n
t h e h o s t s t a t e t a b l e ( T a b l e 2) f o l l o w i n g t h i s l i s t .
,
1 . 1 Send t h e f i r s t block of t h e program r e q u e s t e d , s t a r t t i m e r , e n t e r
Loading s t a t e . I f s e n d i n g secondary code a s a s i n g l e message t h e n
do n o t s t a r t timer and s t a y i n non-MOP s t a t e .
1.2 Determine f u n c t i o n t o be performed.
I f loading, take a c t i o n a s in
1.1; i f dumping, send a Request Memory Dump r e q u e s t , s t a r t t i m e r ,
and e n t e r Dumping s t a t e ; o r i f l i n k t e s t i n g , send a Loopback T e s t
message, s t a r t t i m e r , and e n t e r Link t e s t s t a t e .
2.1 I f r e q u e s t f o r e i t h e r l a s t l o a d number s e n t o r n e x t l o a d , s e n d :
( a ) Memory Load message e i t h e r w i t h o r w i t h o u t t r a n s f e r a d d r e s s or
( b ) send Parameter Load w i t h T r a n s f e r Address i Â l a s t Load and
parameters a r e required.
I f request for another load, r e s t a r t
l o a d i n g from load 0 a g a i n . R e s t a r t timer when s e n d i n g r e s p o n s e .
I f r e c e i v e d Request Load is i n r e s p o n s e t o t r a n s f e r message ( l a s t
l o a d ) t h e n e n t e r non-MOP s t a t e and do n o t s t a r t t i m e r .
2.2 I f t h e MOP Mode Running Message i n d i c a t e s t h a t t h e d e s i r e d
f e a t u r e s a r e n o t p r e s e n t , r e s t a r t l o a d i n g from l o a d 0 . T h i s c o u l d
occur i f t h e s a t e l l i t e r e c e i v e d an i n v a l i d message and d e s i r e d t o
reinitialize.
I f t h e d e s i r e d f e a t u r e s a r e present, then the action described
1.2 s h o u l d be t a k e n .

2.3 Send l a s t l o a d a g a i n , r e s t a r t t i m e r .
3.1 I f more memory is r e q u i r e d t o be dumped t h e n send a n o t h e r Request
Memory Dump, s t a r t t i m e r .
I f l o a d i n g is t o be s t a r t e d , t h e n t a k e
a c t i o n a s d e s c r i b e d under 1 . 2 .
I f l i n k t e s t i n g is t o b e s t a r t e d ,
t h e n t a k e a c t i o n a s d e s c r i b e d under 1 . 2 .
3.2 Send Request Memory Dump a g a i n and r e s t a r t t i m e r .
4.1

I f more l i n k t e s t i n g i s t o be done , send a n o t h e r Loopback T e s t
message and s t a r t t i m e r .
For o t h e r f u n c t i o n s , t a k e a c t i o n a s
d e s c r i b e d under 1 . 2 .

4.2

Resend Loopback T e s t and r e s t a r t t imec

Table 2
Host S t a t e Table
State

Event

New S t a t e

~O~-MOP

Receive v a l i d
Request Program

Load ing

Receive v a l id
MOP Mode
Runn ing

Loading ,
dumping, or
1ink t e s t

Receive v a l id
Request Memory
Load

Loading o r
non-MOP

Receive MOP
Mode Running

Loading ,
Dumping or
Link T e s t

Timeou t

Receive v a l id
Request Program

Load in9

Rece ive Memory
Dump Data

Dumping,
l o a d i n g , or
L i n k Test

Timeout

Dumping

Receive Looptest

Link T e s t

Receive Looped Data

Link T e s t

T imeou t

Link T e s t

Load ing

Dumping

Link t e s t

Act ion

APPENDIX A

EXAMPLES

S a t e l l i t e running ROM
loaded:

A.1

bootstrap

primary

wants

p
-

Events

program

for

Step 1

S a t e l l i t e primary program s e n d s Request Program Message
secondary l o a d e r .

Step 2

Host s e n d s Memory Load w i t h T r a n s f e r
program image.

step 3

S a t e l l i t e s e n d s Request Program f o r o p e r a t i n g system.

Step 4

Host s e n d s Memory Load w i t h o u t T r a n s f e r Address load 0 .

Step 5

S a t e l l i t e s e n d s Request Memory Load 1. Repeat S t e p s 4 and 5
f o r each s u c c e s s i v e l o a d , e v e n t u a l l y t h e l a s t load (number
I
n) is r e c e i v e d with t r a n s f e r a d d r e s s .

Address

secondary

S a t e l l i t e s e n d s Request Memory Load f o r load number
and t r a n s f e r s t o program.

Motes:

,
1

L a s t r e q u e s t is used o n l y t o A C K .

S a t e l l i t e may r e q u e s t t e r t i a r y l o a d e r ( a f t e r S t e p 2 ) which
would t h e n r e a u e s t t h e o p e r a t i n q system.
In t h i s c a s e t h e
l a s t Request Memory Load Message is used and t h e ACK is
omitted.

A.2 Host wants t o
program r u n n i n g )

examine

the

memory

satellite

(secondary
I

Events

Satellite
supported

. s e n d s MOP Mode Runnlnq

1! S t e p 2

Host s e n d s Request Memory Dump.

Step 3

S a t e l l i t e sends Memory D u m p D a t a .

with

dump

11
I

APPENDIX B
DDCMP MAINTENANCE MODE FORMAT

I n t h e DDCMP m a i n t e n a n c e mode, t h e l i n k is d e d i c a t e d t o p e r f o r m i n g MOP
functions.
T h e DDCMP m e s s a g e p r o v i d e s a CRC b l o c k c h e c k o n t h e MOP
d a t a , b u t d o e s n o t p r o v i d e any acknowledgment o f r e c e i p t o r sequence
check.
T h e DDCMP m a i n t e n a n c e mode e n v e l o p e is s i m i l a r i n f o r m a t t o a
DDCMP numbered d a t a m e s s a g e . S e e t h e DDCMP s p e c i f i c a t i o n f o r d e t a i l s
on t h i s f o r m a t a n d o p e r a t i o n . A l l n u m e r i c v a l u e s a r e shown i n d e c i m a l
A l l bytes a r e 8 b i t s long.
DDCMP m a i n t e n a n c e
representation.
messages have t h e f o l l o w i n g format:

Where:
SYNSEQ

T h e DDCMP s y n c s e q u e n c e :
4 or more b y t e s ;
Synchronous l i n k s
Asynchronous l i n k s
none

~ 1 5 0 . (226 o c t a l )

OLE

The m a i n t e n a n c e messaqe h e a d e r s t a r t
octal)

byte;

COUNT

The c o u n t f i e l d
(14
MAINTMSG d a t a f i e l d .

T h e QSYNC f l a q ( 1 b i t ) ;

T h e SELECT f l a q ( 1 b i t ) ;

FILL

A f i l l byte;

FILL

A f i l l byte;

ADDR

The t r i b u t a r y s t a t i o n a d d r e s s b y t e ;
for point-to-point
o p e r a t i o n = 1; f o r m u l t i p o i n t o p e r a t i o n = 1-255.

CRC1

The h e a d e r
CRC-16).

MAINTMSG

The m a i n t e n a n c e messaqe d a t a f i e l d .
m e s s a q e s (COUNT b y t e s i n l e n g t h ) .

Contains

CRC2

T h e d a t a CRC c o m p u t e d o n
( 1 6 - b i t CRC-16).

bits);

number

-144.

(220

bytes

the

1.
1.

= 0.

CRC

computed

DL&

throuqh

(16-bit

ADDR

the

MOP

data

field

only

The MOP m e s s a q e s a r e s e n t w i t h i n t h e MAINTMSG f i e l d w i t h i n
m a i n t e n a n c e mode e n v e l o p e s .

the

DDCMP

the

MAINTMSG

APPENDIX C

PROGRAM TYPES

I n t h e Request Program Message s u b f i e l d PGMTYPE ( s e e S e c t i o n 4.2.5)
t h e g e n e r i c t y p e of program must be s p e c i f i e d . T h i s may be: 0 ( o r
or 2
o m i t t e d ) f o r t h e secondary l o a d e r ; 1 f o r t h e t e r t i a r y l o a d e r ;
f o r t h e o p e r a t i n q system. A b r i e f d e s c r i p t i o n of t h e POP-11 s e c o n d a r y
and t e r t i a r y l o a d e r s is provided below.

Type 0 ( s e c o n d a r y l o a d e r )
The s e c o n d a r y l o a d e r is s e n t i n a s i n g l e
Memory Load w i t h T r a n s f e r Address Message. The secondary l o a d e r must,
t h e r e f o r e , f i t i n t o a s i n g l e message block.
I t is loaded a t l o c a t i o n
6. C u r r e n t secondary l o a d e r s a r e between 400 and 600 b y t e s i n l e n g t h ,
depending upon t h e d e v i c e t y p e used. They use t h e s t a c k a d d r e s s s e t
up by t h e primary l o a d e r . F o r c u r r e n t l o a d e r s t h i s w i l l be between
17400 and 17776. The secondary l o a d e r a s s i g n s i t s b u f f e r s p a c e below
t h e s t a c k . The secondary l o a d e r a c c e p t s Memory Load w i t h and w i t h o u t
T r a n s f e r Address Messages.
I t is, t h e r e f o r e , c a p a b l e of doing
multi-block
l o a d s i n t o a b s o l u t e a d d r e s s e s w i t h o u t memory management.
I t r e q u e s t s a t e r t i a r y boot t o be l o a d e d .

Type 1 ( t e r t i a r y l o a d e r )
The t e r t i a r y l o a d e r is loaded by t h e
secondary i n a multi-block l o a d s t a r t i n g a t l o c a t i o n 10000. I t w i l l
run w i t h memory ma-naqernent on i f
i t e x i s t s on t h e system.
The
t e r t i a r y l o a d e r moves i t s e l f t o t h e t o p of p h y s i c a l memory and a s s i g n s
its s t a c k and b u f f e r s p a c e j u s t below i t s e l f .
I t is, t h e r e f o r e ,
c a p a b l e of multi-block l o a d s from l o c a t i o n 0 up t o its b u f f e r a d d r e s s ,
I t requests the operatinq
u s u a l l y t h e l a s t 1-2K o f p h y s i c a l memory.
system t o be l o a d e d . The c u r r e n t t e r t i a r y l o a d e r s do n o t s p e c i f y any
s p e c i f i c o p e r a t i n q system.
The c h o i c e of system t o
send
is
e s t a b l i s h e d by p r i o r agreement and by command a t t h e h o s t system.

APPENDIX D
REVISION HISTORY

T h i s Appendix p r o v i d e s a l i s t of changes t h a t have been made t o MOP
V e r s i o n 1.1 ( d a t e d J a n u a r y , 1976) and t o MOP V e r s i o n 2.0 ( d a t e d March,
1978)

0 . 1 Changes made t o MOP V e r s i o n 1.1 updated i t t o V e r s i o n 2.0.
changes:

These

Removed a l l r e f e r e n c e s t o MOP b e i n g used d i r e c t l y
to
non-adjacent
s y s t e m s over DECnet l i n k s . The N I C E p r o t o c o l
p e r f o r m s MOP-like f u n c t i o n s w i t h i n DECnet, u s i n g a c t u a l MOP
protocol only over a physical l i n k .

The p r o t o c o l
Decoupled MOP from DDCMP maintenance mode.
s p e c i f i e s t h e r e q u i r e m e n t s of a l i n k c o n t r o l p r o c e d u r e t o be
used w i t h MOP. DDCMP maintenance mode is one such p r o c e d u r e .

D e l e t e d t h e f o l l o w i n g messages n o t needed i n MOP. These a r e
Code 20
Examine d a t a by name. Code 22
now handled by N I C E .
c l e a r d a t a by name. Code 26
Examined d a t a by name.

C l a r i f i e d t h e d e s c r i p t i o n of t h e f i e l d s i n a l l MOP messages.
C l a r i f i e d and expanded t h e o p e r a t i o n a l d e t a i l s of MOP and
added a s t a t e t a b l e f o r o p e r a t i o n .

Added a d e t a i l e d d e s c r i p t i o n of t h e r e q u i r e m e n t s of t h e d a t a
l i n k c o n t r o l p r o c e d u r e t o b e used by MOP and a d e t a i l e d
d e s c r i p t i o n of t h e i n t e r f a c e , s e t o f commands and r e s p o n s e s ,
t o t h a t procedure.

Added VAX and DECSYSTEM 10/20 i n f o r m a t i o n in message
where n e c e s s a r y .

formats

Changed message 8
( R e q u e s t MOP s e c o n d a r y mode program) t o
Request Program.
I t is now used t o r e q u e s t a l l program l o a d s
i n MOP. n o t j u s t t h e s e c o n d a r y program.
The STADDR f i e l d i s
removed and r e p l a c e d by a MOP v e r s i o n number f i e l d . Added
DTE20 t o DEVTYPE f i e l d .
PGMTYPE f i e l d is changed and SOETID
is added.

Changed message 10
Request memory l o a d t o remove NODE and
SOPTID, f u n c t i o n now p a r t of message 8 d e s c r i b e d above.
Added an ERROR f i e l d t o r e t u r n any e r r o r s on p r e v i o u s l o a d .

Chanqed messaqe 1 2
t o MOP mode cunninq from secondary mode
runninq.
Removed S T A D D R and r e p l a c e d w i t h MOP v e r s i o n
number. Added a FEATURES f i e l d t o d e s c r i b e t h e MOP f e a t u r e s
a node s u p p o r t s .

- ..

10.

Added a new message code 20
Parameter load with transfer
addr.
T h i s message is used to load a parameter block before
transferring control to a just loaded program.

11.

Added a detailed. description of primary
operation of loading the secondary program.

mode

and

0.2 Changes made to MOP Version 2.0 updated it to Version 2.1.
changes:
response

Loopback

These
Test

Added Looped Data Message as
Message.

Added host node number parameter
Transfer Address Message.

Added notification from DDCHP that a start was received while
in maintenance mode.

the

Parameter

Load

with

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