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M416-E0300-37622

December 1979

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Document:	DDCMP MULTIPLEXER SYSTEM DESIGN SPECIFICATION AND USERS GUIDE
Order Number:	M416-E0300-37622
Revision:	0
Pages:	62
Original Filename:

OCR Text

DATE:
PROJECT:
CHARGE NO:

12/11/79
nOCMP MULTIPLEXER
M416-E0300-37622

SYSTEM DESIGN SPECIFICATION
AND

USERS GUIDE

·REV 1.1
BY
D.E. KORF

TABLE OF CONTENTS

1.0
1.1
1.2
1.3

INTRODUCTION
PURPOSE
REQUIREMENT SUMMARY
DESIGN GOALS AND CONSIDERATIONS

2.0
2.1

USER VIEW OF SYSTEM
USERS VIEW OF WHAT HAPPENS

3.0
3.1
3.2
3.3

PDP11 INTERFACES
BUFFER DESCRIPTOR LIST (BDL) DEFINITION
CSR INPUT COMMANDS TO KMC
CSR RESPONSE COMMANDS FROM KMC

4.0
4.1
4.2
4.2.1
4.3
4.4
4.5
4.5.1
4.5.2
4.5.3
4.5.4
4.5.5
4.5.6
4.5.7
4.5.8
4.5.9
4.5.10
4.5.11

KMC INTERNAL DESIGN
SECTION OVERVIEW
DETAILED EXAMPLE OF MESSAGE TO BE TRANSMITTED
DETAILED INTERNAL VIEW OF INTERACTIONS
MEMORY DEFINITION
BLOCK DIAGRAM OF THE SYSTEM
TABLES, QUEUES AND BUFFERS
LINE STATUS TABLE
LINE OUTPUT STAT~TABLE (LOST)
LINE INPUT STATE TABLE (LIST)
CSR QUEUES
NPR INPUT REQUEST QUE
NPR OUTPUT REQUEST QUE
MESSAGE CHARACTER ADDRESS BUFFERS
MESSAGE WAITING RESPONSE QUEUE
RETRANSMIT QUEUE
INTERMEDIATE DATA BUFFERS
CONTROL MESSAGE QUE

APPENDIX A
APPENDIX B

RELEASE NOTES
SYSTEM STATES.

1.0

INTRODUCTION

1.1

PURPOSE
The purpose of this document is to provide a design
overview of KMC DDCMP multiplexer and its interaction
with a host PDPll processor. It is also 'intended to
provide the PDPll user with the required knowledge to
interface the PDPll host to the KMC multiplexer.

1.2

REQUIREMENT SUMMARY
Detailed below is a summary of the Requirements, Goals
and non goals of the DDCMP multiplexer. The Functional
Specification should be referred to for a complete
definition of multiplexer functionality.
KMC DOCMP MULTI-LINE CONTROLLER

WHAT ARE THE MAJOR OBJECTIVES OF MULTIPLEXER?
Provide 8 lines at 'full or half duplex with'speeos
up to 9600 BPS.
DDCMP communications protocol implemented in
firmware providing high reliability and throughput
with low host processor overhead.
Provide communications between KMCll and other
synchronous interfaces that support DDCMP protocol
in a point to point environment.
16 Bit NPR (DMA) transfers for minimum interference
with host processor operation.
F-irmware based on KMCII-B so that the firmware is
loadable.

WHAT ARE ITS GOALS?

Line level compatability with present DMClI.
Support greater than seven (7) outstand'ing
messages.

WHAT THE MULTIPLEXER IS NOT
Not a DMClI modified to JUST scan 7 more lines.
Will not provide support of line speeds greater
than 9600 BPS.
Will not support local on board diagnostics.
(Note: Since KMC is loadable, diagnostics can be
separately loaded into the KMC).
'
Will not support automatic recovery from powerfail.

DESIGN GOALS AND CONSIDERATIONS
CSR control is the same as COMM rOP-DUP.
Note commands differ but interface control is the
same.
CSR transfers from KMC to host PDPll take priority
over CSR transfers from PDPll to KMC.
Body of all messages reside in PDPlI host.
All message headers reside in KMC.
All inquiry control messages reside in KMC.
System is primarily a state system.
The states in the -system are controlled by a series
of queues, tables and buffers.
Data reception takes priority over data
transmission.
Attempt to make the system somewhat self regulating
(It won't accept more work than what it can
handle) •

1.3

DESIGN GOALS AND CONSIDERATIONS
Listed below are some design considerations of the DOCMP
multiplexer in relation to other products, interfaces
and internal control. The speed calculations define the
max.imum slice of time or state size that may be executed
for each line per character per second.
SPEED CALCULATIONS

KMC = 5,000,000 instructions per second.
CHARACTER RATE = 8 lines X 9600 BPS
8 bits per character

= 9600 characters/second

INSTRUCTIONS/CHAR/SEC = 5,000,000 instr/sec = 520.8 instr/char/sec
9,600 char/sec
520.8 instructions/character/sec for 1/2 duplex line.
NOTE:

The 520.8 instruction/character/sec is for a one way
(l/2 duplex) line to arrive at a full duplex two way
communication divide 520.8 by 2.

FULL DUPLEX = 520.8 = 260 instructions/character/second
2

2.0

USERS VIEW OF SYSTEM
Below is a visual description of the system from the PDP1l
users point of view. All major components of the system are
identified.
VISUAL DESCRIPTION OF SYSTEM

I 6 BUFFER TO TRANSMIT
I~-----~-------~--~------~
I 7 APPLICATION
I-~---~----------------~~-

1-------I B.D.L.I

1..·-------

---------------~---~--J
UNIBUS
--------~----~--~---~-J

I 1
---I 2

KMC
MEMORY

D
R
I

V
E

--------------------------

I 3

1 - LINE STATUS TABLE IN KMC (LST)
CONTAINS CURRENT LINE DEFINITIONS
2

LINE OUTPUT STATE TABLE IN KMC (LOST)
CONTAINS CURRENT STATE, HEADER AND
NEXT CHARACTER INFO

3 - INTERMEDIATE BUFFER IN KMC (IB)
CONTAINS BUFFER OF 8 CHARACTERS
TO BE TRANSMITTED
4 - DRIVER INTERFACE IN PDPll
5 - BUFFER DESCRIPTOR L-IST AREA IN PDPl1
6 - DATA BUFFER TO BE TRANSMITTED
7 - APPLICATION PROGRAMS

PDPll
MEMORY

2.1

USERS VIEW OF WHAT HAPPENS
The following is a description of the general processes
that occur from a users point of view in the
transmission of a message. The reception of a message
has a similar process to that of transmission.
WHAT HAPPENS

I 6

BUFFER TO TRANSMIT

I----------------------~-f 7 APPLICATION
I-------~-----~-~--------I-~-----I B.D.L.I
5
1----.... --D
I
R
I
4
PDP;tl
I
V
I
MEMORY

----------------------1
UNIBUS
----------------------1I

I
I
t

---------

----~--~-----------~
I LST---1 1
!(MC
I LOST I 2 MEMORY
lIB.

Application program (7) passes to driver (4) a request
for ·a message to be transmitted. It specifies the BDL
MEMBER (5) that contains the address and character count
of the buffer to betransmitt~d.
The driver (4) passes the information to the !{MC.
The KMC first builds the header information in the
L.O.S.T. Table (2).
The KMC then retrieves the BDLMember (5) which defines
where in PDP memory the data buffer (6) is and how big
it is.
The KMC then retrieves the first eight characters of the
data buffer (6) and places them in the intermediate
buffer (1).

The KMC then transmits the header information from the
L.O.S.T. (6) table and updates the line status table
(3) •

After the header has been transmitted, a header eRC is
transmitted.
Following the header CRC transmission, a character is
retrieved from the intermediate buffer (1) and
transmitted and a character from the data buffer (6) is
requested to take its place (remember 7 other characters
will be t~ansmitted before the character requested is
transmitted). The L.S.T. (3) is updated as is required.
The previous step is repeated until all characters have
been transmitted. the data CRe is then generated and
the LOST (2) is updated.
Upon reception of an ACK or NAK, (after seven retries),
the BDL (5) member is set as free and a notification is
sent to the driver (4) as to what has happened and the
KMC tables and buffers 1,2,3 are updated.
The driver (4) then passes the KMC response status to
the application program.

3.0

PDPll INTERFACES
This section discusses the interfaces between the KMC
and PDPll. There are three areas of interaction. The
Buffer Descriptor List Definition Table in the PDPlI,
CSR Input Commands to the KMC from the PDPll and CSR
Response Commands from the KMC to the PDPll.

3.1

BUFFER DESCRIPTOR LIST (BDL) DEFINITIONS
In the PDPII an ~rea must be set aside to hold
definitions of messages to be transmitted or received.
What is a Buffer Descriptor List? It is a four word
entry in PDPll memory that defines to the KMC and the
PDPl1 where in PDPII memory a data message is," how many
characters are in the message, the line number and
tributary of the line the message is to be tr'ansmitted
or was received on, "the DDCMP message number that was
assigned by the KMC protocol handler and the status of
the four word BDL entry (member). During initialization
a BDL base address is passed to the KMC which defines
where in memory the BDL Definition table starts. All
references to this area of memory after setting the base
is by member (four word entry) number. It is up to the
user to define the size of this area. Its minimum size
must be large enough to handle the number of input and
output lines~ For an eight line full duplex operation,
the minimum size would be 64 words. That is eight lines
for input at four words per line and eight lines for
output at four words per line, assuming all lines are
transmitting and receiving data at the same time. A
definition of the Buffer Descriptor list and how it is
organized follows.

PDPll BUFFER DESCRIPTOR LIST DEFINITION TABLE

ADDRESS

X+l
X+2
X+3
X+4
X+S
X+6
X+7

X+(N*4-4)
X+(N*4-3)
X+ (N* 4-2)
X+(N*4-l)

I STATUS
I
I
IBUFFER START ADDRESS
I
I I NUMBER OF CHARACTERS 14 BITS I
1 MESSAGE I __~I~__________~I
'STATUS
I
I

MEMBER 1

r-BUFFER~S~TA~R~T~A~D~D~R~E~S~S------~I

I INUMBER OF CHARACTERS 14 BITS I MEMBER 2
LMESSAGE 1_----:11.....-_ _ _ _ _...:..1

I STATUS
I
I
IBUFFER START ADDRESS
I
1 1NUMBER OF CHARACTERS 14 BITS I
i-MESSAGE 1
I
I

MEMBER N

MESSAGE t

= DDCMP Message Number from KMC Controller

STATUS

= The status area is for use' by the PDPl1
for keeping track of which BDLs ar~ in

use and assigned to transmit and receive
lines which are free.
BUFFER START ADDR = Start Address of Message Data to be
Transmitted.
LENGTH

= Character Count of Message to be

Transmitted.

Length of BDL list is user defined.

Maximum of 256 members.

3.2

CSR INPUT COMMAND TO KMC
The KMC and PDPl! communicate with each other via
Control Status Registers (CSRs). Since both the KMC and
PDPll can read and write the CSRs, a control mechanism
is required to prevent one CPU from writing while the
other CPU is reading.
All input commands to the KMC are issued by an
application program to a driver program which is
completed in a series of steps. The driver·program sets
RQl to request the use of the CSRfor transfer of data
and then waits for the RMC to set RDYl. This wait can
be implemented through a delay loop or can wait for an
interrupt. The delay loop is not recommended. The KMC
will then set RDYl when it is ready to accept an input.
After the RDYI has been set by the KMC.
The PDPl1 driver loads the CSRs with the command and its
assoc iated parameter·s.When the parameters have been
loaded into the CSR, the RDYI is cleared to inform the
KMC that the parameters may be read.
There are four (4) major input command types to the KMC.
The command types and CSR structures are defined in the
following figures.

KMC CONTROL INPUT COMMANDS

GENERAL FORMA'!'

14. 13

BJI BESERVm NOT
tISE:D
TRIBUTARY NO.

LINE NUMBER

COMMAND

IEI

StmCODE

NO'!'

PASSWORD/BDLAODRESS

PASSWORD!BOL ADDRESS
....

......"...~/

. 'ro 'lPANSMIT .
COMMAND ~ES
COMMAND

COMMAND

VALUE

DESCRIPTION

Master Control

LineControl'-

Message Control

3·

st.atus

MASTER CONTROL COHHANDS
COMMAND

COMMAND

·COMMAND

VALUE

SOB CODE

DESCRJ:P1'ION

~itSystem

N/A

Reset/Set to. DDCMP Mode

LN' , TRIB •

Enter HOP Mode

PARAMETERS

LN t, TlaBI,
PASSWORD

0
0

6
7

Ter.minateActivity
Set Line Scan Length
(No. of Lines to Scan)
Set HOP Mode Password
for ForceaEntry
Set BDL Base Address

Set Modem CSR Address
. (Note ~ also enables
modem . control for all
lines.
* Currently not planned for implementation.

LNt, TRIB

LN.

LN ., PASSWORD

BDL ADORESS,
'l'RANS., RCV.
CSR Address of

modem· control
l~we~_ . 18

bits

LINE CONTROL COMMANDS
COMMAND
VALUE

COMMAND
SUB CODE

1
1
1

DESCRIPTION
Set Line Up
Set Line 1/2 Duplex
Set Line Down

PARAMETERS
LN # (TRIB #)
LN #
LN # (TRIB #)

MESSAGE CONTROL COMMANDS
COMMAND
VALUE

COMMAND
SUBCODE

DESCRIPTION

Transmit Message

LN i,BDL Member
i of messages,
TRIB #

BDL Member for use
in Message Reception

BDL Member,

PARAMETERS

LINE i

STATUS CONTROL COMMANDS

COMMAND
VALUE

COMMAND
SUB CODE

DESCRIPTION

Request Line Status

(LN

ReadKM'C Memory

KMC Data Mem'ory
Address

write KMC Memory

KMC Data Memory
Address & Value
to be stored.

(Note an automatic
read of the data
store will take
place- for verification.
*Currently not implemented.

PARAMETERS
i, . (TRIB #1) )

I<MCCONTROL l:NPOT COMMANDS

RESET/SET DDCMPMODE

5·

HlN __ . _ ...

1'RZBC'TARY NO.

'lEI

LINE NDMBER

N01'

•

EMC CON'l'ROL INPUT COMMANDS
ENTER MOP MODE

14·13

KIN __ ..__

.~RIBOTARY NO.

IE!:·.

'. LINE .NOMBER

,
PASSWORD CB.A.MCTElt2

PASSWORD CHARACTER 1

PASSWORD CB.A.MC'l'ER 4

PASSWORD CHARACTER 3

XMC CON'l'ROL INPUT COMMANDS

TEBHINA'l'E .~~IVI'l'Y

14. 13

87654

NOT

EMC CONTROL INPO'l' COMMANDS

SET LINE SCAN LENGTH

87· 6

iQI ReSER\1!!DNOT

tJSED

3
COMMAND

·St1SCODE

NO.OF LINES '.to

:tEI

KMC CONTROL INPUT COMMANDS
MODEM CONTROL CSR ADDR

TRIBUTARY NO.

LINE NUMBER

ADDRESS MIDDLE 8 BITS

RJI

RESERVED NOT
COMMAND
lEI
USED 1 SUB ODE 1

NOT RESERVED ROY! ~

'ED

NOT CCM-WID
E CODE :

Me CONTROL INPUT COMMANDS
BOL BASE ADDBESS

14· 13

SOL ADDRESS MIDDLE 8 BITS

87654

LOWER 8 BITS OFBDL :SASE

mc CON'l'ROL INPtT'l' COMMANDS
SE~

14. 13

LINE UP

3
:tEl·

TRIBUTARY NO.

XMC CONTROL INPO'l' COMMANDS

SE'l' LINE ~ DUPLEX

RJI RESER\lED NO'l'COMMANl)

BON .,...._11. ..
TRIBO'l'ARY NO.

OSED

LINE Nt1KBER

NO'!'

S.UBCODE

I;EI

XMC CON'l'ROLINPO'l' COMMANDS

SE'l'LZNE DOWN

14. 13'

7
~

~..

TRIBUTARY NO.

LINE NTJMBER

\3LCEi!CEk,ft.'IP\ NO'!'
~v..., CSED

3
COMMAND

StlBCODE

IEI

mc CONTROL INPOT COMMANDS
TRANSMIT MESSAGE

3
COMMAND
SOBCODE

SDL MEMBER NO.

me CONTROL INPUT COMMANDS
SOL MEMBER FOR OSE IN MESSAGE RECEPTION

13·

HJN

"aJI BESIE2VEO

LINEN'OMBER "

NO'!'

4
NO'!'

tlSED

OSUBSODE 1

coMMAtm

IEI

KMC CONTROL INPUT COMMANDS

READ KMCll DATA MEMORY

RON

RJI

RFSERVED

NOT
USED

NOT
US

MAR PAGE

MAR LOW

IEI

KMC CONTROL INPUT COMMANDS
WRITE KMCll DATA MEMORY

RON

NOT
COMMAND
lEI
R'JI RESERVED USED
OSUB· ODE 0

TRIBUTARY NO.

NOT

CCMWID

DE .

DATA BYTE

bC CONTROL J:NPOT COMMANDS

REQUEST LINE S~ATOS

14 · 13

RON
t.rRnOWUtY NO.

•

BJI

IRESERVED OSED

LINE NUMBER . Ncr.t'

1:1OT

3
. COMMANJ)

SOBCODE

I~I

3.3

CSR RESPONSE COMMANDS FROM KMC
Corresponding to the CSR input commands there are a
series of output commands. Commands from the KMC to the
PDPllalways take priority over an input command
request. The method used for implementing output
commands are as follows:
The KMC loads the CSRs with the parameters required for
a given command;
theRDYO bit is set and an interrupt is generated to the
PDPll indicating thePDPll should read the CSRs:
the driver programs retrieves the CSR data and clears
the RDYO bit to indicate the transfer is complete.
There are four (4) major output command types. from the
KMC. The command types and CSR structures are defined
in the following figures.

1Q1C CON'1'ROL 00'1' COMMANDS
GENERAL FO:RMA~

14. 13

876
.......

KJN a- ..__

IEO

3
COHMAND • NOT
StmCODE

trSED

'mIBt11'ARY NO.

BDL·MEHBER
. NO.
.

MESSAGE NO. /ltEASON

COMMANl)"ftPES
COMMAND

VALUE

DESCRIPTION

o·

Positive Responses ControlNegative Bespoztses.Control
Message Reception Control
Status Responses

1
2

(Does Not Ose General Format for Out Commands)

POSTIVIE RESPONSE CONTROL
COMMAND
VALUE

COMMAND
SUB CODE

0
0
0
0
0

0
1

DESCRIPTION
Init Complete
Set/Reset Complete
Activity Terminated
MOP Mode Entered*
Message Acknolwedged

3
4

PARAMETERS
N/A
LN #, 'TRIB t
LN i, TRIB i
LN i, TRIB :3
Message i, BDL t

NEGATIVE RESPONSE CONTROL
COMMAND
VALUE

COMMAND
SUBCODE

Error Threshold
Reached

LN i, TRIB t

Messaged Naked

LN i, TRIB i,
BDL Member

Returned too many
receiver buffers
for line

LN i, MEMBERt

DESCRIPTION

PARAMETERS

MESSAGE RECEPTION CONTROL
COMMAND
VALUE

COMMAND
SUBCODE

Message Received

LN ',TRIB i,
BDL MEMBER MSG t

Request BDL Member
for Reception of
Message

LNi

DESCRIPTION

PARAMETERS

STATUS
COMMAND
VALUE

COMMAND
SUBCODE

1st 4 bytes of line
status table for
specific line.

LINt TRIB
Bytes 0-3 of LST
for line.

Last 4 bytes of
line status table
for specific line.

.LINt ·TRIB
Bytes 4-7 of LST
for line.

Dump of specified
KMC Data Memory

Oata Memory
Address & Contents

DESCRIPTION

PARAMETERS

DC CON'l'ROLOU'l' COMMANDS

INITIALIZATION COMPLETE

14. 13

4
IEO

COMMAND

NOT

SOBCODE

1JSED

COMMAND TYPES
COMMAND VALUE

g
1
2

DESCRIPTION

Positive "Responses Control
Negative Responses Control
Message Reception Control
Status Responses - (Does Not Use
General Format fo~ Out COIllIlland~)

I<MC CON':ROL 00': COMMANDS

SET/RESET COMPLETE

15
BON

a-._ . .

TRIBUTARY NO.

lEO
LINE NtlKSER

COMMAND

SOBCODE

NO'!'
CSED

DC CONTROL OUT COMMANDS

ACTIVITY TE~NATED

14. 13

87654
NOT

'l'RIBtl'I'ARY NO.

lEO

3
COMMAND

Ncn

SUBCODE.

OSED

KMC CONTROL OO~ COMMANDS
MESSAGE ACKNOWLEDGED

87654

NOT
tJS!D

LINE .NOMBER

BDL MEMBER NUMBER

MESSAGE NUMBER

I01C CONTROL OOT COMMANDS
SET/RESET FAILED

15
KlN ......._ ....

87'
NOT

4
IEO

3
COMKANJ)

SUSCODE

'.rRIBOTARYNO.

....

EMC CONTROL OOT COMMANDS
ERROR THRESHOLD REACHED

14. 13

RlN ........_ ....

:IEO

,.'
NOl'L
KJ!O PJ:ISERVEC
.

3
NOT,

tlSEd

TABLE OF CONTENTS

1.0
1.1
1.2
1.3

INTRODUC'l' I ON
PURPOSE
REQUIREMENT SUMMARY
DESIGN GOALS AND CONSIDERATIONS

2.0
2.1

USER VIEW OF SYSTEM
USERS VIEW OF WHAT HAPPENS

3.0
3.1
3.2
3.3

PDP11 INTERFACES
BUFFER DESCRIPTOR LIST (BDL) DEFINITION
CSR INPUT COMMANDS TO KMC
CSR RESPONSE COMMANDS FROM KMC

4.0
4.1
4.2
4.2.1
4.3
4.4
4.5
4".5.1
4.5.2
4.5.3
4.5.4
4.5.5
4.5.6
4.5.7
4.5.8
4.5.9
4.5.10
4.5.11

KMC INTERNAL DESIGN
SECTION OVERVIEW
DETAILED EXAMPLE OF MESSAGE TO BE TRANSMITTED
DETAILED INTERNAL VIEW OF INTERACTIONS
MEMORY DEFINITION
BLOCK DIAGRAM OF THE SYSTEM
TABLES, QUEUES AND BUFFERS
LINE STATUS TABLE
LINE OUTPUT STATE TABLE (LOST)
LINE INPUT STATE TABLE (LIST)
CSR QUEUES
NPR INPUT REQUEST QUE
NPR OUTPUT REQUEST QUE
MESSAGE CHARACTER ADDRESS BUFFERS
MESSAGE WAITING RESPONSE QUEUE
RETRANSMIT QUEUE
INTERMEDIATE DATA BUFFERS
CONTROL MESSAGE QUE

KMC CONTROL OUT COMMANDS

MESSAGENACKED

14. 13

87'

3
COMMAND
SOBCODE

lIJN a -.._ ....
..

t.rRIB01'AltY NO.

LINE NmmER

SDL MEMBER ~~ER

m, .~, ~

REASON

N01'

OSED

!(MC CONTROL
OOT COMMANDS
.
.
TO MANY RECEIVE BUFFERS

14. 13

4
lEO

TRIBUTARY NO.

LINE ·.NTJMBER

BDL MEMaER.NUMBER

3
NO'!'
T.lSED

KMC CONTROL OUT COMMANDS

STATUS RESPONSES FORMAT 1

NOT-

- RON

TRIBUTARY NO.

lEO
a»m.ND

LINE NUMBER

. .LINE 'STATUS'

LINE FLAGS - ..
..

:. ":NEXT -MSG

# 1£0 BE:.TRANSMITTED·

TEMP.DATA

STATUS RESPqNSES FORMAT 2

NOT
'.rRIBOTAltY NO.

.
#- .MSGS RECEIVED

lEO

LINE NUMBER
# ACKRCVD FOR MSG·SENT
•• '"'0 . . . .

iNAKS SENT

COMMAND
NOT
SUBCODE =1 USED

tNAKS: ~cRCVD

KMC CONTROL OUTPUT COMMANDS
READ KMCll DATA MEMORY

Nor'

MAR PAGE

MAR LOW
DATA BYTE

l(MC CONTROL OUT COMMANDS
MESSAGE RECEIVED

7
NOT

~RIBOTAltY

654

lEO

LINE NOMBER

NO.
-

, -

BDL MEMB~R WOMBER

MESSAGE NUMBER

NOT
tlSEC

4.0

KMC DESIGN

4.1

The KMC DDCMP multiplexer is a state driven system,
based on a series of queues, tables and buffers. Each
state per line is less than or equal to 260 KMC
instructions. The following sections describe the KMC
memory organization, tables and queues used in the
operation and control of the multiplexer.
The secion starts out with a detailed example of a
message transmission and steps involved. This is
followed by a memory map, and block diagram of the sytem
and definition of tables. The last section contains a
definition of various states the system may be in.

- 4.2

DETAILED EXAMPLE OF MESSAGE TO BE TRANSMITTED
1.

Application program passes-to driver BDL Base
address.

PDPll driver passes BDL base to KMC.

Application program request a transmission of a
message providing PDPll Driver with BDL member
control address of message data and. numbe.r of
messages to be transmitted.

PDPll Driver requests CSR transfer.

KMC acknowledges request when input que is
available.

KMC retries CSR/Retransmit data and places data in
input.

KMC command interpreter sees input data in queue.
It determines from queue data line data is to be
,t'ransmitted on. If line is busy., it leaves data in
que and waits to check it next time around. It
then dertermines if a control message is in the
control out que. If so, it is prepared for
transmission. Else it sets the line to output
state I and places CSR data into output me sage
charac·ter address buffer • The command interpreter
state is then sat back to O.

The KMC then waits unt-il select flag is set.
set, the KMC then builds the message header.

TheKMC then builds a BDL address and places a read
request into the output NPR queue and set BDL flag.

10.

The KMC then performs THE NPR states which request
the BDL Read.

11.

After completion ,of the read, the message address
contained in the BDL is placed in. the Output
message character address table.

12.

An output.request is placed in the NPR queue to set
the BDL as in unuse by the KMC.

13.

The!(MC then requests that the first four words 8
character of the message be stored in the
intermediate buffer.

14.

After eight characters are buffered, the LST is
updated, the header of the message is then
transmitted.

15.

After the header and eRC of the header is
transmitted, the first character of the da~a
message is transmitted.

16.

After every even character of the message has been
transmitted from the intermediate buffer, an NPR
INPUT QUEUE request is made to get two more
characters from the PDPll for transmission until
entire message has been retrieved •
•

17.

At this point in time, if multiple messages
(pipelined messages) are to ~e transmitted, the
next BDL address is calculated the BDL and next
message flags are set and th. address of the next
message is retrieved. An NPR INPUT queue request
is then made for a charcter pair of the next
message while the current message is finishing its
transmision.

18.

Upon completion of the transmission of the message,
the message pending flag is set and the BDL member
i, line t and tributary t are placed in the message
waiting response que.

19.

If the message is acked, then the entry in the
message pending que is cleared. A request is
placed in the OUT NPR Queue to release the BDL. A
transmit complete eSR output request is placed in
the eSR output que.

20.

If the message is nacked,the entry in the message
pending que is removed and placed in the 'retransmit
que. An error counter is then incremented.

21.

Before another eSR request is honored from the 11,
the retransmit que is emptied and goes back for
retransmission.

PDPll ..

.
DC 'rBANSMI'l'S HEADER
FROM LINE STATE QUEUE

------ ---~l

FROM IDl

. .

RETRIEVES CBABACTER

PLACE IT IN 'l'RANSMIT'l'ER
AND TRANSMIT

.
1

BE'rRIEVE CBABAC'l'ER

FROMID

I
I
. I·

PLACE IN TRANSMITTER

___ .____ ...lI
I

t
I

!
I

REQUES INPUT NPR QUEtJE
I
CHARACTER 1 ' R A N S F E R J

,- - - - - - -NPR IiREQUES

I
I,"

1---"'--------'"I'.rB
"I '
1
"
'... -.- - -- --..,
I

r.! .

BUILD NEJb. MESSAGE CHARACTER
ADDRESS ~OFFER

L_J~I-''''' - - - - - J

\....._-----.

PLACE BDL MEMBER, LN t,
TRIB i, MSG i IN WAITING.
RESPONSE QUEUE

,. -- - ·WAIT

' '--"'1

POPll

WAI'r
•

:- I

I
"I

I
I

I
I
I

~ ~ FRpM WAI'!' :RESPONSE
I

+
PLACE IN RETRANSMIT QUEOE

,
I

----"
\ (Retrans. priol:ity over CSR Queue)
'--- -.'+
,

I WAI'!' COMMAND INTERPRETER
I

RETRANSMIT MESSAGE

---------~
UPDATE LST ACK/NAK
I

I
~

NPR OOTPUT REQUEST QUE
BOt. MEMBER
RELEASED
- - - - I

- -

... UPDATE BOL LIST

REQUEST CSR OUTPUT QUEUE TRANSFER
a
I

'l'YPE., MSG

I, BDL MEMBER - - - - - - -;. PDPll DRIVER ACCEPTS
PARAMETERS

APPLICATION PROGRAM

4.3

MEMORY DEFINITION
.0

777

LINE STATUS TABLE (LST)

1000

- 1077

LINE OUTPUT STATE TABLE (LOST)

1100

- 1177

LINE INPUT STATE TABLE (LIST)

1200

- 1277

INTERMEDIATE TRANSMIT BUFFERS(ITB)

1300

- 1466

SPARE

1467

- 1477

CSR INPUT BUFFER

1500

1677

CONTROL MESSAGE OUTPUT OUE

1700

- 2077

CONTROL MESSAGE INPUT QUE

2100

- 2207

PRIMARY OUTPUT MSG ADDR BUFFER

2210

- 2317

SECONDARY OUTPUT MSG ADDR BUFFER

2320

- 2427

PRIMARY INPUT MSG ADDRESS BUFFER

2430

- 2547

SECONDARY INPUT MSG ADDRESS BUFFER

2550

- 2777

SPARE

3000

- 3377

NPR OUTPUT REQUEST QUE

3400

- 3777

MSG WAITING RESPONSE QUEUE 1ST HALF

4000

- 4377

NPR INPUT REQUEST QUEUE

4400

- 4777

CSR OUTPUT QUEUE

5000

- 5110

TIMEoRS

5111

- 6977

SPARE

6400

- 6777

MESSAGES WAITING RESPONSE QUEUE 2ND HALF

7000

- 7640

RETRANSMIT QUE

7640

- 7661

KMC DATA VARIABLES

~.4

LINE SE~CT

BLOCK DIAGRAM OF SYSTEM

bENERAL

~OUSE

INPUT
SCAN

FLEANING
~ND

AAIN'l'.

NPR.';;·.

NPR

STATES

- .............

STATES

----------'.

.......

CSR

---....STATES

_..

....

....____
.11..._ _. . -_ _ _ _- . . '.

, IF

DLE
STATES

ENO
STATEE}

<II'

SOH
STATES
...

REQUEST

NPR

...

. STATE

1
. REQUEST
OUTPUT
MESSAGE

EXECUTION
COMMAND

REQUEST
NPR/CSR
FUNCTION

...

••

REQUEST
NPR/CSR

REQUEST
NPR/CSR
FUNCTION

FUNCTIO~
I

NPR

agQUEST
REQUEST
OUTPUT •
MESSAGE l1li

REQUEST
OUTPUT I
MESSAGE

REQUEST
OUTPUT
MESSAGE

CSR
REQUEST
l . t - _....___

MEMORY LAYOUT
LINE STATUS TABLE

MEM ADDR
TRIB t
LINE t
LINE 0

TRIB 1
TRIB 2
TRIB 3
TRIB 4
TRIB 5
TRIB 6
TRIB 7

LINE 1
TRIB 1
TRIB 2
TRIB 3
TRIB 4
TRIB 5
TRIB 6
TRIB 7

LINE 7

TRIB 1
TRIB 2
TRIB 3
TRIB 4
TRIB 5
TRIB 6
TRIB 7

0
0

0
0
0
0
0
0
0
0

1
1

0
1

0
0
0

1
1

0
0
0

1
2
3
5
6
7

0
0
0
0

0
0

0,
0

7
7
7
7
7

3
4
5
6
7

123 4 5 6 7

1 2 3 45 6 7

1 2 34 56 7

0
0
0
0

LINE TRIBUTARY ENTRIES

o = LINE/TRIB STATUS

= LINE/TRIB FLAGS
2 = FLAGS
3 = NEXT MESSAGE TO BE

TRANSMITTED

4 = NUMBER OF ACKS RECEIVED
= NUMBER OF MESSAGES RECEIVED
6 = NUMBER OF NAKS TRANSMITTED
7= NUMBER OF NAKS RECEIVED

LINE STATUS BYTE MEANINGS

BYTE

NAME

BIT t

LINE
STATUS

BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7

LINE
FLAGS 1

BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5'
BIT 6
BIT 7

DEFINITION
0
0
0
0
0
0

= LINE DOWN
= DDCMPMODE
= XMIT NOT ACTIVE
= RECEPTION NOT ACTIVE
= NO START PENDING
SPARE
= FULL
o=
DUPLEX

1 = LINE UP
1 = MOP

0 = NO START RCVD
0
NO NAK RCVD

=
0 = NO REP RCVD
0 = NO XMIT CONTRO MSG
0 = NO ACKRCVD
0 = NO STACK RCVD

1 = START RCVD
1 = NACK RCVD
1 = REP RCVD
1 = XMIT CONTROL MSG
1 = ACK RCVD
1 = STACK RCVD

0 = NO START PENDING

1 = ACTIVE
1 = ACTIVE
1 = START PENDING
1 = SPARE
1 = 1/2 DUPLEX
SELECT FLAG FOR 1/2 DUPLEX TURN AROUND
0 = NO 'XMIT

= START PENDING

TEMPORARY DATA

MSG tFROM ACK OR NAK

NBRNXT

NEXT MESSAGE NUMBER TO BE TRANSMITTED

NBRACK

NUMBER OF ACKs RECEIVED FOR MESSAGE SENT

NBRRCV

NUMBER OF MESSAGES RECEIVED

NAKRCV

NUMBER OF NAKs RECEIVED (NO OVERFLOW)

NAKXMT

NUMBER OFNAKs TRANSMITTED (NO OVERFLOW)

4.5

TABLES AND QUES AND BUFFERS

The following sections provide definitions of the
Tables, Queues and Buffers used internally by the KMC11.
4.5.1

LINE STATUS TABLE (LST)

The line status table is used to reflect the current
status and definition for each line. The table is
configured of 64 entries at 8 bytes of information per
entry. The entries consist of 8 lines with 8
tributaries per line. The line table·entriescan be
thought of as a series of row entries. The line number
and line tributary number make up the memory address of
where the table entry for a given line is to be found.
The line status table contains the following
information:

* Current line status up/down
* Current mode DDCMP/MOP
* Transmitter state
* Receive state
* Full or 1/2" duplex line
* Select flag
* Next message number to be sent
* Number of ACRs received for message sent
* Number of messages sent
* Number of NAKs transmitted
* Number of NARs ~eceived

4.5.2 LINE OUTPUT STATE TABLE

(L.O.S.~.)

The Line Output State Table consists of eight subtables. One for
each output line. Each subtable contains eight entries which contain
the current state of the line and the header of the current output
message except CRC values. The first byte of each subtable is the
current state of the line. This state value is used as an indexed
branch to execute the =next series of instructions to keep the line
operating properly. The remainder of the table contains the header
data of the current message being transmitted.
LINE OUTPUT STATE TABLE
LINE
TRIB
STATE
ADDR

BASE
BDL

BASE
LOW
3

HDR2

HDR3

HDR4

CRC1/NEXT
CHAR IN

CRC2/NEXT
CHAR AVAIL.

1000

1010

STATE

2
BDRl

1077

BASE
UP

WORK
BDL

BOL

* MSGS

LINE OUTPUT STATE TABLE CONTROL MSG
1
234
5
STATE ACK t LSTL LSTH INDEX

6
NAK COUNT

4.5.3 LINE INPUT STATE TABLE (L.I.S.T.)
The Li~e Input State Table is configured exactly as the Line Output
State Table except that it is used for input rather than output.
LINE INPUT STATE TABLE
STATES
AD DR 1100

2
HDRI

3
HDR2

HDR3

HDR4

STATE

.
1170

CRCI/NEXT
CHAR IN

CRC2/NEXT
CHAR AVAIL •

.4~5.4

CSR QUEUE

The CSR functions have been broken down into Input and Output States
and Ques. There can be only cine CSR state at any given time. If
there is both an input request and an output request, the KMC output
request takes priority. There are eleven (11) output queue entries
and one input que entry. See Section 3.2.3.3 on control in and
control out commands for specific CSR control information.

CSR OUTPUT QUE ENTRIES
BYTE

= SUBCOMMAND
= LINE &TRIB #
2 = DATA BSEL 3
3 = DATA BSEL 4
4 = DATA BSEL 5
0

5 = DATA BSEL 6
6 = COMMAND TYPE

CSR INPUT QUEUE
BYTE

= COMMAND (BITS 0,1)
= SUBCOMMAND (BITS 2,3,4)
2 = LINE # (BITS 0-3) & TRIB # (BITS 4-7)
3 = BDL ADDRESS MIDDLE BYTE/DATA .
4 = BDL ADDRESS LOWER BYTE/DATA
5 = BDL ADDRESS UPPER 2 BITS (6,7)/MEMBER NO. BITS 0-7
0

= # OF MESSAGES TO BE SENT.

4.5.5 NPR INPUT REQUEST

The NPR input request queue is the only interface that allows NPR
input transfers between the KMC and the PDPll. There are two basic
types of input NPR transfers in the system: message data and B.D.L.
data. To request a BDL transfer, the line number is entered into the
NPR Que with BDL bit set (bit 4) and with either the primary or
secondary message character buffer bit set (bit 5). Bits 0-3
indicate the line number that is requesting the transfer and point tc
the message character buffer u~ed. Bit 4 if on requests that the
contents be placed not in the intermediate buffer for the line, but
in the message character address buffer. Bit 5 indic~tes whether the
BDL data is to be in the primary or ,econdarymessage character
address buffer. For a simple message character input only, the line
number is entered and the retrieved data characters are placed in the
intermediate buffer for the requesting line.
4.5.6 NPR OUTPUT REQUEST QUEUE

The NPR output request que operates similar to that of the input
request. The queue is structured rather differently: there are threE
bytes per entry verses the one (1) in the Input Request Que. The
first byte the line number has the same definition as that of an
Input Request. The second two bytes are the character pair or data
that is to be stored.

NPR CHARACTER INPUT REQUEST QUEUE

LINE'

LN.

LINE #

ENTRY 1

ENTRY 2

ENT.3

ENT. 15

ENTRY 16

LINE

NPR CHARACTER OUTPUT REQUEST QUEUE

ENTRY 1

CHARACTER A

CHARACTER B

ADDR

CHARACTER" A

CHARACTERB

ADDR

ENTRY 2
ENTRY 3

ENTRY 16

4.5.7 INPUT/OUTPUT MESSAGE CHARACTER ADDRESS BUFFERS
The Output Message Character Address Buffers are the main interface
to the NPR queue. These buffers contain the address of where the
next two characters for transfer from the PDPll are stored.,· It also
contains the character count of the message and the count of the
number of characters retrieved from the PDPll. The tributary number
and current message transmit number are also stored in this buffer.
An example of its use is after a character pair is transmitted, the
line number is placed in the input NPR queue. The input NPR 'queue
accesses the output message character address buffer to find the
address of the next character pair to be transmitted.
There are four message character address buffers - two (2) for input
a'nd two (2) for output. Th'=e reason for redundancy is to save time
during pipelined input or output messages. The "next" Input/Output
Message Character Address buffer is readied during use of the primary
buffer. As soon as the primary buffer is complete, a buffer flip
flop takes'place and the secondary is now the primary buffer
interface for transmitting or receiving characters.

OUTPUT DATA CHARACTER ADDRESS BUFFER
BYTE
LINE 1
LINE 2
LINE 3

TRIB 31 BOL ADDR
1
1
I
I

•

LINE 8

CHAR COUNT I t OF CHAR IBOL tl t OF
I TRANSFERRED I
I MSGS
I
I
I
1

I
I

INPUT DATA CHARACTER ADDRESS BUFFER

BYTE
LINE 1
LINE 2
LINE 3

BDL t

BDL ADOR
I

CHAR COUNT I t OF CHAR IODD BYTEt
I RECEIVEDS I RECEIVED'

I'
I

.
LINE 8

I
I
I

WAITING RESPONSE BUFFER

ENTRY 1
ENTRY 2
ENTRY 3
•
•
•

ENTRY 100

LINE t

TRIB t

MSG t

IBDL MEMBER I
I.
I
'I
I

I
I

LINE t

TRIB t

MSG#

IBDL MEMBER I

I
j

4.5.8

MESSAGE WAITING RESPONSE QUEUE
After a message has been transmitted, its line number, tributary
number, message number and BDLnumber are entered into the waitin
response queue. This queue is a holding area containing all
pertinent information concerning the message until the message
disposition can be determined. If the message is acked, the BDL
member is released, the queue entry cleared, and the PDPll is
notified of the transmit. If the message was naked and seven
retries have not occurred, the queue entry will be cleared and tl
data will be entered into the retransmit que.

4.5.9

RETRANSMIT QUE \
This queue contains informatidn required to retransmit a message
that was NAKED or failed to get an acknowledgement. This queue j
examined and takes priority over the CSR input 'request que from
the PDPll.

4.5.10

INTERMEDIATE TRANSMIT BUFFER
There is one intermediate buffer per line in the system. This
buffer area provides an input buffering function between
characters being sent from the PDPll. The ITB keeps eight (8)
characters buffered ahead of the transmitter such that if a
transfer of a character is late in coming from the PDPll, the KMC
will not have to wait and will transmit the seven (7) previously
buffered characters before the one that arrived late. The ITB is
used in conjunction with the NPR INPUT request que.

INTERMEDIATE TRANSMIT BUFFER
ADDR

120
121
122

DATA

DATA
n

2
3
rATA DATA
II

•

•
•
•
•

127

•

4
~
n

DATA DATA

7
DATA

456

,ft

INTERMEDIATE RECEIVE BUFFER
ADDR

130
131
132
•

•
•
•

137

012

mTADATADATADATADATADATAmTADATA

4.5.11

CONTROL MESSAGE QUEUE
The control message queues are used to hold control
messages that are to be transmitted as soon as the line
is free. There are two (2) queues - one for input
message reception and the second is for message
transmission. Position in the queuedefi~es line and
tributary, thus entry nine in the que Is for line one,
tributary one. To determine the line and tributary
number, the queue entry is divided by eight. The
integer from the dIvision gives the line number and the
remainder is the tributary number. Each queue entry is
two bytes long_ The first byte defines the message type
and the second the subtype.
,..

LINE 0

Type

LINE 0 LINE 1

O,S Bi'b Type
S~

LINE 4
~

4.6

LINE 5 LINE 5
Type
SUb~

LINE 1 LINE 2
Sub1YPe Type

LINE 3 LINE
~ '-'Ype

LINE 6 LINE 6
Type
~

Type

LINE

•

LINE 7
SubType

SYSTEM STATES
·The following sections contain a list of the various
states the multiplexer may be in. It should be noted
that it is possible and very likely that ~he KMC will be
in several different states at any given point in time.