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DEC-12-511B-D

August 1969

28 pages

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Document:	LINC-8 Simulator Trap Processor
Order Number:	DEC-12-511B-D
Revision:	0
Pages:	28
Original Filename:	http://bitsavers.org/pdf/dec/pdp12/diagnostics_set2/DEC-12_SI1B-D.pdf

OCR Text

-c

PDP-12
LIBRARY

LINC-8 SIMULATOR TRAP PROCESSOR

Order DEC-12-SllB-D from Program Library, Digital Equipment
Corporation, Maynard, Massachusetts 01754

Price $1.00

Direct comments concerning this document to:
Software Information Service
Digital Equipment Corporation
Maynard, Massachusetts 01754

C'.
i

CONTENTS
Page

Abstract

Equipment and Storage Requirements

2. l

Equipment

2.2

Storage

Loading, Starting and Restarting

3.1

Loading Procedure

3.2

Normal Starting Procedure (Start 400)

3.3

Starting Procedure for Immediate GUIDE or LAP6-3L
Loading and Starting (Start 20)

3.4

The Instruction Trap Enable Flip-Flop

3.5

Norma I Restart (Start 400)

3.6

"User 20" Restart (Start 20)

3.7

GUIDE Load Restart (Start 700-717)

Program Operation

4.1

Illegal Teletype Characters

4.2

Undefined Instruction Error Stop

Internal Operation

5. l

Overview

5.2

Console Starts and Restarts

5.3

Operation of the Instruction Trap Hardware

5.4

Machine State Saving

5.5

Instruction Identification

5.6

TYP Processing

5.7

KBD Processing

5.8

Return To User Program

LINC-8 Simulator Trap Processor Adoptions

6. l

Adaption To Process Additional LINC-8 OPR's

6.2

Example: Operating the XY12 Plotter Control with LINC
or LINC-8 OPR's

6.3

Adaption for Convenient Trap Processor Loading from GUIDE
or LAP6-3 L Tapes

6.4

Adaption for Convenient Loading With a User Program From
a DIAL Tape

iii

0
CONTENTS (Cont)

6.5

Adaption for Loading of Programs Other Than GUIDE and LAP6-3L
By The Trap Processor

6.6

Adaption to Suppress Teletype Character Echoing

Assembly Listing

If"-,
1'·,

'--·/

ABSTRACT

The LINC-8 Simulator Trap Processor handles Teletype input and output for LINC-8 and classic LINC
programs when they ore run on the PDP-12. It must be loaded into the PDP-12 core memory with any
LINC-8 or classic LINC program which uses the keyboard, or any classic LINC program which uses the
Teleprinter, in order for that program to run on the PDP-12.
The trap processor operates by using the PDP-12 Instruction Trap Facility to detect execution of either
of the two LINC-8 Teletype input/output instructions by the user's program. It responds to user's
execution of o Teletype instruction by executing coding to simulate the instruction's LINC-8 or classic
LINC effect. After simulation of the instruction, the trap processor returns control to the user program.
Users may easily adapt the LINC-8 Simulator Trap Processor to their own purposes. Explicit instructions for o number of useful adoptions are provided in this document, along with enough information on
the internal operation of the program to permit users to easily implement adoptions of their own invention. In this connection, attention is directed to the Dispatch Table Trap Processor, DEC-12-SI2A.
It is a more suitable starting point for building extended trap processors which process a large number
of different trapped instructions than is the LINC-8 Simulator Trap Processor.
An important limitation of the trap processor i> that it is not interruptible. It may not be operated
when the PDP-12 Program Interrupt is enabled.
This document applies to the machine readable program version bearing software product code
DEC-12-Sll B-UA.

EQUIPMENT AND STORAGE REQUIREMENTS

2. l

Equipment

The LINC-8 Simulator Trap Processor is at present distributed in LINCtape form only, and therefore
requires o PDP-12 with LINCtape control and at least one TU55 DECtope/LINCtape transi:-ort for
program loading. The program itself will run on a minimum PDP-12.
The program operates correctly both in 4K PDP-12's and in PDP-12's having any amount of extended
memory up to the 32K maximum total. Instruction traps originating in extended memory will be processed no differently than the same instruction traps originating in basic memory.

0
\

0
2.2

Storage

The program occupies most of the locations below 462, plus locations 700 to 717, all in PDP-12 memory
segment 0.

LOADING, STARTING AND RESTARTING

3. 1

Loading Procedure

The program is distributed on a DIAL tape. Load and start that copy of DIAL, and type into DIAL,
iu1 U'iSJM,1/1)

(The symbol i means Teletype LINE FEED.

) means CARRIAGE RETURN.)

The LINC-8 Simulator Trap Processor will be loaded from the DIAL tape into the PDP-12 core memory,
and the computer will halt.

3.2

.,-,

Normal Starting Procedure (Start 400)

Press 1/0 Preset, and then Start 400. The program will turn on the Instruction Trap Enable Flip-Flop

\l_,.;

and halt with the Instruction Field set to 2 and the Data Field set to 3. Verify that the Instruction
Trap Enable Flip-Flop is on by observing the console TRAP indicator. This indicator should be lit. If
it is not, some kind of error has occurred. The error may be either a machine error or an operator

error. Reload the trap processor and try again.
Now read in the user program. If the program is located on some specific block(s) of a LINCtape,
mount the tape on either transport and execute an appropriate tape instruction from the console as if
the machine were a LINC or a LINC-8. If the user program is a named file on a LAP6-3L or GUIDE
tape, mount the tape on unit 0, set the LOCAL-OFF-REMOTE switch to REMOTE and press CONT.
GUIDE or LAP6-3L *will be loaded, and the user program may be recalled using the usual GUIDE or
LAP6 program loading procedure.
If the user program is on paper tape, read it in and start it using the usual paper tape loading and
starting procedures, as described in the Binary Loader operating instructions, DEC-08-LBAA-D.

*LINC-8 and LINC users will recall that the GUIDE program starting procedure may be used with :
either GUIDE or LAP6-3L.

Switch the processor mode to the PDP-8 mode by executing the PDP instruction (octal :0002) before
using the Binary Loader.

Mode changing through use of I/O Preset in conjunction with the console

Mode key should be avoided because I/O Preset clears the Instruction Trap Enable Flip-Flop.

3. 3

Starting Procedure for Immediate GUIDE or LAP6-3L Loading and Starting (Start 20)

To automatically load and start a LJNC-8 GUIDE or LAP6-3L tape along with the trap processor, load
the trap processor from the DIAL tape as directed above, and !hen press I/O Preset, Start 20, rather
than 1/0 Preset, Start 400. A GUIDE or LAP6-3L system will be read in from unit 0 and started.
This procedure duplicates the "Start 400" procedure given above, with the exception that the computer ,
doe~ not halt between the trap processor initialization and the loading and starting of the GUIDE or

LAP6-3L system.

3.4

The Instruction Trap Enable Flip-Flop

Once a user program has been read in and started, the machine behaves like a LINC-8 or classic
LINC with respect to Teletype input and output thereafter, but only if the Instruction Trap Enable
Flip-Flop has been set. The PDP-12 Instruction Trap Enable Flip-Flop must be set in order for the
trap processor to work. The state of this flip-flop is indicated by the TRAP light on the computer
console. If the trap processor is loaded exactly as directed above, and if the user program is operated
exactly as its instructions direct, the Trap Enable Flip-Flop will never be cleared, and will cause no
problems. However, in practice it is sometimes cleared (by the operator pressing I/O PRESET for
example), so some convenient methods for resetting it are included in the trap processor program in the
form of the following restart procedures.

3.5

Normal Restart (Start 400)

If the Instruction Trap Enable Flip-Flop has been cleared, it may be set again (providing the trap
processor has been loaded into core as directed above) by starting at location 400 in memory segment 0
(absolute address 00400). Note that the START 400 key may not be used for this unless the Instruction
Field (IF) is set to 0 because START 400 takes the high order 5 bits of the starting address from the IF.
Set 0400 into the Left Switches and use START LS, rather than Start 400. Use of this entry point seh
the Trap Enable Flip-Flop and halts the computer. (Setting of the Trap Enable Flip-Flop may be confirmed by observing the console TRAP indicator.) Pressing continue after the computer has halted
causes a transfer to location 400 in memory segment 2 (ab~olute address 04400), with the Data Field
set to 3.

0
,

3. 6

"User 20" Restart (Start 20)

Starting at location 20 in memory segment 0 (00020) sets the Trap Enable Flip-Flop and immediately
transfers control to location 20 in memory bank 2 (absolute address 04020), with the Data Field set to
3. Note that the START 20 key may not be used for this unless the Instruction Field (IF) is set to 0
because START 20 takes the high order 5 bits of the 15 bit starting address from the IF. Set 0020 in the
left Switches and use Start LS, rather than using START 20.

3. 7

GUIDE Load Restart (Start 700-717)

A third alternative is to start at any location between 700 and 717 in field 0. Use of any of these
e~try points sets the Trap Enable Flip-Flop and then loa'ds and starts the LINC GUIDE or LAP6 system

(if an appropriate tape is mounted on transport 0 and the LOCAL-OFF-REMOTE switch is set to
REMOTE).

PROGRAM OPERATION

Once the LINC-8 or classic LINC user program and the LINC-8 Simulator Trap Processor have both
been loaded into PDP-12 memory, the operating instructions for the user program apply, and the user
program will behave as it would on a LINC-8 or classic LINC, and no special account need be taken

of the fact that a PDP-12 rather than a LI NC-8 or classic LI NC is being used. There are a couple of
minor exceptions to this. The PDP-12 console operates slightly differently from the LI NC-8 console
and the classic LINC console. Also, the characters which in the LINC are obtained by striking the
CASE key and then some other key such as . ,= andE3are obtained in the PDP-12 by striking a single
Teletype key. The Teletype keys which are used to obtain the various LINC codes are indicated in
the following diagram of the Teletype keyboard.

0 Q CD ~ CD CD CD G) Q Q 0 0 ®

@QQG)QG)QG)G)QG)@@
8QQG)QQQQCDQ0@88
8Q e> 0 Q G) wwoo oe
I
I
SPACE

Figure 1.

location of LINC keys on the Teletype keyboard

An additional exception to strict classic LINC compatibility concerns "echoing" of keyboard characters.
Characters typed into a user program running with the trap processor are automatically printed on the
Teleprinter by the trap processor. Instructions for suppressing this feature are given in Section 6.6,
Adaption to Suppress Teletype Character Echoing.

4. 1 Illegal Teletype Characters
Some teletype keys, such as the semi-colon key, are not used for any LINC characters, either standard
or special. These keys should not be struck when the trap processor is being used to run LINC or
LINC-8 programs.
up arrow, "t".

If one of these illegal keys is struck, it is printed on the Teletype preceded by an

Control is not returned to the user's LINC-8 or classic LINC program until a legal

character is struck.
The following Teletype keyboard characters are illegal:

! ' II, TAB, (, ) *, ? ,
f

4. 2

] , t, ;, <, >.

Undefined Instruction Error Stop

The trap processor halts al location 130 in memory segment 0 when any instruction other than a Teletype

(

input or output instruction is given. The trapped instruction is contained in the accumulator, and the
address of the instruction is in location 134 of memory segment 0.

INTERNAL OPERATION

5. l

Overview

Teletype input·-output in LINC and UNC-8 program5 involves only three instruction>: Keyboard
(mnemonic KBD; instruction code 515), Type Out (mnemonic TYP; instruction code 514) and Key Struck
(mnemonic KST; instruction code 415). These are the only Lll'~C-8 instructions whose operation
involve> the LINC-B Simulator Trap Processor. The proces'.;ing performed by the LINC-8 Simulator
Trap Proces>or for tlie KBD and TYP imtructiom consist<. of detection of their execution by the user
program, and execution of programming to reproduce in detail their LINC-8 or classic LINC effect.
The KST instruction is a skip instruction which skips when the Teletype keyboard flag is set. This flag
is set by the hardware when the operator strikes a Teletype key. The trap processor clears it when there
is no keyboard character available for the user program to read in.

0
Processing for the trapped instructions KBD and TYP consists of three steps. Processing is initiated by
the occurrence of an instruction trap. The first step consists of the identification of the instruction
causing the trap. The second step is the execution of programming to simulate the LINC-8 effect of
the particular trapped instruction. The final step is the return of control to the user program.
Jn addition to the "trap processor proper", which performs as described above, the program as distributed contains small amounts of code to implement the various console restarts described above.

5.2

Console Starts and Restarts

The program is initially loaded into memory segment 2, and relocates itself into segment 0 as soon as
it is started. This technique is used because it leads to a particularly simple procedure for loading the
program directly from LJNCtape using the console functions. See Section 6.3, Adaption for Convenient Loading of the Trap Processor from GUIDE and LAP6-3L Tapes, for a description of this procedure. If
the routine had to be loaded into segment 0 directly, the console procedure for loading it would be more
complicated than it is because the operator would have to set one of the 5-bit Field Registers to 0 before
execution of the tape read instruction in order to load data into segment 0. As is, the user may initially
load the program into any memory segment for which memory is physically present.
Both the "Start 20" and "Start 400" program starting procedures execute the trap processor relocator

routine at symbolic location SETUP. This routine relocates the trap processor from the current instruction field into memory segment 0.

Notice that the relocator routine is not itself relocated, since it is

u5ed only once. After the trap processor has been relocated, the locations 700 through 717 are filled
I

With "JMP GUIDE". This operation provides for restarting of the GUIDE system using the Start Left
S~itches function when any tape instruction is set into the Left Switches.

5.3

Operation of the Instruction Trap Hardware

The trap processor operates with the Instruction Trap facility enabled, so execution of any trappable
instruction (except tape instructions) by the user's program causes a transfer of control to location 141
in memory segment 0 (absolute address 00141). Also, the low order 12 bits of the address of the
instruction following the trap instruction is stored in location 140, and the contents of the Instruction
Field and Data Field when the trap occurred is stored in the Save Field Register.

( -,,...

5.4

Machine State Saving

The instructions between 140 and symbolic location FETCH saves regi>teVi and indicators whose contents
wi II be affected by the operation of the trap processor. They wi II be restored before control is returned
to the user program. Notice that the Overflow flip-flop and memory location 0 are both saved. They
are both affected by the operations in the trap processor.

5. 5

Instruction Identification

The code from ~ymbolic location FETCH to 0Pl4 obtains the instruction cau>ing the trap and transfers
control to the subroutine which performs the LINC-8 function of the particular instruction.

5.6

TYP Processing

TYP and TYP I (OPR14 and OPR I 14) are processed identically, by the subroutine beginning at OPI14.
Note that exit from the subroutine does not occur until the Teleprinter has completely finished printing
the character. This assures that the printer will be ready to accept a new character the next time the
subroutine is entered.

5.7

KBD Processing

The routine begins at tag OPlS and ends just before tag INIT. It has three functions. The functions
are interrelated and are not performed in any simple sequence by the routine. Consequently, the
following discussions of them do not reference specific pieces of code within the routine.
The first function performed is the translation of ASCII character code characters into LINC character
code characters. (Part of the definition of the LINC KBD instruction is that characters which are read
in by the instruction have the LINC character code.) This translation sometimes requires that two
characters be passed to the user program when only one Teletype character has been typed. Some
LINC "special" characters (?, =-, u,,,.,

, [, _, :) did not have their own keys, and existed only

by virtue of the convention that the "CASE" character followed by some other character was to be
interpreted as a "special" character. The Teletype keyboard has a "SHIFT" foci lity whereby a single
key may generate more than one character code, and, because of its ease of use, this "SHIFT" technique rather than the "CASE key" technique is used in the PDP-12 (and also the LINC-8) to generate
the "special" characters. But since LINC programs "expect" to have special characters entered as two
characters, and in general have no provision for accepting them in any other way, the trap processor
must generate the appropriate pair of characters in response to the use of a single Teletype key.

0
The second function of this routine is the interpretation of the I bit. This bit, when raised, means,
"Don't execute the next instruction until a character from the keyboard has been acquired. If no
character has been typed, pause unti I the user types one. "
The final function of the routine is the clearing of the keyboard flag. This is the flag which is sensed
by the LINC KST instruction. Note that when two LINC characters are generated in response to one
Teletype character, the flag is not cleared unti I after the second LINC character has been generated.
This assures that the user program will "think" that the operator has struck the second character, and
wi 11 execute the KBD i nstructi o.n which col Iects that second character.

5. 8

Return to User Program

The routine to return control to the user program begins at symbolic location RET and ends at OVN.
The routine is entirely straightforWard. It simply restores the various registers in the machine to their
values prior to entry to the trap processor. Note that when the KBD instruction has been given the AC
w.ill get filled with some character code rather than with its contents at the time of trap processor
entry.

L!NC-8 SIMULATOR TRAP PROCESSOR ADAPTIONS

6 '' I1

Adaption to Process Additional LINC-8 OPR's

LlNC-8 and classic LINC installations often use instructions of the LINC OPR group for purposes other
than control of the Teletype. For example, an installation may use OPR's 5, 6, 7, 10, 11and12 for
controlling pen motion on an incremental plotter.

Each OPR causes the pen to move one increment in

one of six directions. In this section, we indicate how the LINC-8 Simulator Trap Processor may be
"custom tailored" to process additional OPR's or other trapped instructions. Jn general, such modifications involve three steps:
a. extension of the trapped instruction identification routine to recognize trapped instructiom
other than the Teletype OPR's
b.

addition of a routine to simulate the effect of the LINC-8 or LINC OPR instruction; and

return of control to the user program.

The extension to the trap identification routine consists simply of adding instructions to transfer control
to a subroutine when one of the new OPR's is recognized. The new instructions should be added at

j
I

symbolic location OTHERS, and care should be taken to preserve the error stop which occurs when the
trapped instruction is not recognized.
A routine which is entered when the new OPR's are given must be added to the program. The details
of this routine are entirely dependent on the character of the new OPR.
Finally, the user program must be re-entered. This is accomplished by transferring control to symbolic
location RET.

6.2

Existing coding attends to the detai Is of restarting the user program.

Example: Operating the XY12 Plotter Control with LINC or LJNC-8 OPR's

Suppose that a LINC-8 or LINC user is operating an incremental plotter with 6 OPR instructions which
work as follows:
OPR
OPR
OPR
OPR
OPR
OPR

5 (0505)
6 (0506)
7 (0507)
10 (0510)
11 (0511)
12(0512)

- lower pen
- raise pen
- move drum up 1 unit
- move drum down l unit
- move pen right 1 unit
- move pen left l unit

Suppose further that each OPR "pauses" until the completion of the plotter operation caused by its
execution. That is, execution of an OPR is not completed, and execution of the following instruction
does not begin until the plotter operation caused by the OPR is completed. This "paused" mode of
operation obtains whether or not the instruction's I bit is set.
The XY12 plotter control used the following PDP-8 mode commands:
PLSF
PLCF
PLPU
PLPR
PLDU
PLDD
PLPL
PLPD

(6501)
(6502)
{6504)
(6511)
(6512)
(6514)
(6521)
(6524)

- Skip on Plotter Flag
- Clear Plotter Flag
- Pen Up
- Pen Right
- Drum Up
- Drum Down
- Pen Left
- Pen Down

The plotter flag is set by the completion of a plotter command affecting the pen or the drum. It is
cleared by the PLCF command only. The pen and drum command:; do not affect the plotter flag.
The following modifications to the LINC-8 Simulator Trap Processor will enable it to run LINC or
LINC-8 programs which operate the plotter in the manner described above:

C·

....

~-~-~--~--

. . . .----··,ri.>.."l:,"';'- ,.,_.,_., ._. .,._,.,., . . . .,. . . . .

--~""""',,,,.,..,,...,_~~-~-

~-"'"'-""'"·'·

0
1.

Replace the instruction at symbolic location OTHER with the following instruction:
nTHER,

JMP PLOT

2. Add this subroutine to the program iust after symbolic location ENDX. (Actually, the
routine could be inserted anywhere before TABE, which is the last location loaded into memory
segment 0 by the loading sequence.)

I
/SIJHI~

TO klll\I XYJ~'. CO[\ITkOI
/MO!lF: llS I Nfi H<APPEIJ OPF<.'>.
Pl OT,
STf\ 1
Pl. INST,
0
BCL

FkOM I.JN(;

ADA I
-OPR-12
APO
JMP PLERF<
ADA I
6
APO
JMP PL ERR
A Of\ T
ADD Pl .TAH-1
STC • +I
HI T
PI fiCJ
STC
Pl Ji'

/Sf\V~

JNSTF<UCTJON

/JGi\!OkE

li\ISTklJCTif1['I

HIT

/OPR
/NO.

12 OR LESS?
ERROR

/YES.
/OPF<
/NO.

/YFS.

OK SO
5

~~?\f<

cm MORE?
Ekf<OR
OHTr1JN COIV1Mf\i\llJ

/H FC OMLS

f\ JJJJ

P L.T/\H

l'-1

fJMOIH~

Pl r; O,

Pl CF.
HLT

PLSF
JMP • - I
1 l i\JC

LMODE
/f~ETlJk[\J

JMP RET
I
/INSTRUCTION
PL ERR,

PL TAB,

NOT RECOGNIZED
LOA
PL.INST
JMP ERR
PDP
PM ODE
PLPD
PLPU

p J_i) u
PUllJ

Pl Pl<
I' I PI

USER

/DO ERROR STC1P

/PEN DOWi\J. DPk
/pf,~N UP
/Df<UM DO~JM
/J)]<LJM UP
/Pl·.l'J HIGHT
/J-'l<'f'.J U·l·T .f!PI<

1;·

I I f·Jf:
I f"ifl!JI·

These modifications are most easily made by modifying the program's source and reassembling the program, as opposed to manually inserting the new instructions from the computer console.

0
!

6. 3

Adaption for Convenient Loading of the Trap Processor from a GUIDE or LAP6-3L Tape

A particularly convenient way of using the trap processor with an existing GUIDE or LAP6-3L tape is
to copy the program in exactly its present form onto some otherwise unused tape blocks and subsequently
load it directly from these tape blocks using console functions. The advantage of this loading procedure
is that it involves only the tape with the programs which are to be run with the trap processor. No
separate DIAL tape is required for program loading purposes.
Procedures are given below for copying the trap processor onto a GUIDE or LAP6-3L tape and for
subsequently reading it back into core for use with a LINC or LINC-8 program. Note that the program
is stored in pairs of blocks which begin at blocks having block numbers which are multiples of 10 - e.g.,
blocks 10 and l l, or 230 and 231. This is done so that the tape group instructions WCG and RCG may
be used to effect the tape operations involving the programs.
Notice also that this procedure may be used with LINCtape5 other than GUIDE or LAP6-3L tapes.
Procedure to Copy the Trap Processor onto a GUIDE or LAP6-3L Tape:

c.·

Load the Trap Processor from a DIAL tape using the usual procedure.

Press I/O Preset.

Mount a GUIDE or LAP6-3L tape on unit 0.

Set in the Left and Right Switches:
Left

Right

0705

lXXO

(XXO is the first tape block of the pair of hloc.ks in which the program is to be stored.)
5.

Press DO. The Trap Processor will be written into the designated tape block.

Procedure to Load the Trap Processor from a GUIDE or LAP6-3L Tape:
1.

Press STOP.

Mount the GUIDE or LAP6-3L tape on unit 0.

Press I/O Preset.

Set in Left and Right Switches:
Left

Right

0701

lXXO

(XXO is the first tape block of the pair of blocks onto which the program has been copied.)

Press DO. The Trap Processor will be read into memory segment 2.

Press Start 20. The Trap Processor will relocate itself from segment 2 into segment 0 and
the GUIDE or LAP6-3L System will be loaded and started.

0
6.4

Adaption for Convenient Loading with a User Program from a DIAL Tape

The LINC-8 Simulator Trap Processor is designed to be loaded into memory ahead of user programs.

normal use, it is loaded into memory segment 2, and relocates itself into segment 0 as soon as it is
started in order to leave segment 2 free for user programming. It is not difficult to modify the trap
processor so that it may be loaded directly into segment 0. This modification may be made in the
assembly source of the program, and this modified source may be assembled along with a DIAL source
of the user program. Such a source may be obtained from a LAP6 source through use of the program
CONVERT. The resulting program may then be filed and retrieved from LINCtape as a single binary
program. However, once the program is loaded from LINCtape, one of the trap processor restarts
must be executed in order to initialize the trap processor and set the Instruction Trap Enable Flip-Flop.
Production of a source modified for segment 0 loading consists of the following three steps:
l.

Insert the pseudo-op SEGMNT 0 before the first line of code in the source program.

2. Replace the instructions in location 20 and symbolic location RST400 with "JMP INIT".
This step prevents entry to the trap processor relocating program.
3. Delete all instructions after symbolic location TABE. These instructions comprise the trap
processor relocation routine, which is no longer needed.

6. 5

Adaption for Loading of Programs Other than GUIDE and LAP6-3L by the Trap Processor

It is easy to modify the trap processor to load programs other than GUIDE or LAP6-3L when using the

automatic loading and starting feature. The code which implements the load and start feature begins
at symbolic location GUIDE+ 1. It is quite straightforward:

r;t I 1 J) I·.,

.JM!'
l. IJI"

J f\J IT

11r·1lT1 /\I I tr.. Ti<f\f'

R DC
1 LJvrn
LDF '..l
LIF 2
DJR
JMP

l'l<ULI· ;;;.,()H

/ffr(\I)

(JlJ]IJF

;_;·rn1n hLOCK

/INTO OUARTER 1, SEGMFNl

I L100

/START GU IDE

As on example, suppose that the trap processor is to be used with a LAP6 version other than LAP6-3L.
Suppose the LINC-8 or classic LINC console procedure for loading and starting the other LAP6 version
consists of executing the double-word tape instruction RCG 7300, and then pushing "START 20". The
trap processor will perform this operation if the code at symbolic location GUIDE is replaced by the
following:

c·

GUJDF,

JMP

INIT

LDF
LOA

fRAP

PROC~SSOR

/PUT RCG 73Vl0 IN
//101 (:, J'.\NU LJ0 l 7

RCG
;_; T f\
~01

/JNITJALIZE

I flf\
1:rn0
;_; T f1
;; V11 7

LOF
I lF
ciMP

I JUHP

LJO l f.,

The instruction RCG 7300 is inserted into locations 16 and 17 in memory bank 2 - i.e., 4016 and
4017 - and is immediately executed from these locations.* The next insl·ruction is taken from location
4020. This is the starting location of the program.

6.6

Adaption to Suppress Teletype Character Echoing

The trap processor echoes characters typed by the computer operator on the console teleprinter in
addition to transmitting them to the user program. This character "echoing" may be suppressed by
removing seven instructions beginning at symbolic location LOOl. After modification, the section of
the program near LOOl should look like this:

I Ill>,

STC

(\(;

STC

\JI-'(;

I"l FrJk TkA~l~H k
1r;JH1k tUT fJVJ·I~ bUrFFk

PIT

/k r~f\IJ C Hf\k f\ ~JI J
/CL Ff1k Kl,CYH0/1k!J Flfifj
/kr_ TlJI-rn TO USFR PROGRAM

/ST (JkF.

IOR
KR Hf\
1 r 1r1 J ,
JM!-'
I
/TL LE GAL CHARACTF.R
RETX,
LOA

/PRINT UP ARROW.

*One might ask here, "What happens if the RCG im.truction fails at, say, block 301 ? The computer
will try to execute the RCG again from the beginning, but the instruction will have been destroyed by
the arrival in core of block 300." The answer is that when the PDP-12 tape control retries an instruction, it does not read the instruction from core a second time. It uses the same data it obtained when
the instruction was read initially.

""1

n (1 ·.:
' ' • i '\J ·C· .. t r'\!
N ¢ I"- 0 •O ' J ..() ¢ <t ,!\
t\l ..~ (\J"" "' 1 ~ ~ ~J l':'.l C'J
-O<t <t<t"1"' <¥<¥

r-... "

(\J I") <t

'°'°"'

""'

<-:;;:
Xod'<t

,.... ,_ i.... 1-

(';>

:>!';lt<;>

-"> 1- N "'

W<>"<(

ro ro w i... u

WW:f'.:11)1- WI-->- <<-llnO..
IX: D:: Q'. a: er VJ V> VI >- >- t- t- -:::>

----- -

4242
CDFX
4171
DOKBD 425r
ENDX
4.36?
ERR
41.3,:
F'ETCH 416!
GOMAN .a472
GRC
4262
GUIDE 403S
!NIT
4356
KBD
0515
KCCA
6032
KRBA
6036
KRSA
6034
LC
4225
LOO
432:5
L001
4327
LOW
4317
LP
4255
M70
4135
ONE
4136
CPR
0500
OP14
4212
OTHERS 4211
OVL
4222
OVN
4247
PC
4134
PRINT 4.550
Q
4232

0
-~er-

--~---------

0
·~

------ ---

-------

(

0472
0473
0474
0475
0476
0477
0500
05 01
0502
0503
0504
0505
05.:16
121507
05Hl
0511
0512
0513
0514
0515
0516
0517
0520
0521
0522
11!523
0524
0525
0526
0527
0530

0472

060ii

GCJM~N,

'1473

b~33

.'.474

k:Jl5 7

Jt-<P
/THIS LANDS IN FIELD 0
GUIDE
/TRAP PROCESSOR RELOCATOR
SETUP,
SET
17

LI~

~475

z, e ~tC

i476

102 ~'.

LOA

;:4 77
iS Jic.'

6356

.; '.'!?

1fJ 4£

ST A

0?Zl

[~~~e·

2il

522

4025

252'3

STC
LDF

(' 1

2504

C640
0361

ei~~,

7334

~506

kJvl 62

0507

2017

Vl510

2263

0511
0512
0513
0514
0515
e516

k:'017

2517

0520
0521
0522
0523
0524
0525
J526
0527

1023
1062
0221
6512
0062
2677
0061
7757
1020
6033
1062
0221
6524
6017

/SET UP RESTARTS
IN IT
/SET UP 20 RESTART
RST400
0

SET I 1
-TABE+17
SET l 2
2017
SET I 3
17
LOA I 3
STA I 2
XSK l 1
,-3
JMP
SET I 2
2677
SET l 1
-20
LOA
JMP
GU IDE
STA
2
I
XSK l 1
,-2
JMP
JMP
17

/SET UP 400 RESTART
/SET DATA FIELD TO 0
/SET UP MOVE COUNT
/SET TO-ADDRESS
/BIT 1 <2~010) SAYS USE OF
/SET FROM•ADDRESS
/BIT 1 (0°000) SAYS USE IF
/INCREM, 3,GET (3)
/INCREM.2,STORE C2l
/INCREM, 1, SKIP IF 1=1777
/1 NOT 1777, LOOP AGAIN
/SET UP FOR LEFT
/SWITCHES RESTART
/20 JMP GUIDE S
0

/INC 2, STORE INTO <2>
/END CHECK

0373
0374

(')

0375

..
" .... .._ ...

0376

" ... ""' c

121377
12140121
041211

:' .:..; ~

04:212

~ ~

0403

c -.

r.::1404
041215

0406
0407
041121

. 0411
121412

)

,,-

'")

.... . . .

~ ..: ~- .;

~...;

...

(

·1 ~

:.... ...

TA81

:.. .) -:':-

-=-::;:

.., : .... :-

7676
2376
76:4
7670

7676
7676
7656
7676
1276
7676
767 6
7676
7676
7676
7676
7676
2376
7614
7676

<:: 2::i 5

2265

62:5
:676
7 76

6215
1676
7676

~-'

..... i.

: ~ ... ::-;
/

-:;it-

<-'

4: .3

.., :; i t

t.).

41, .!

-6- 0
..,::: ~
.., 6 7 ~

: ~::::
r~ .! :. ~

0413

:· 4:.,
;: 42

0415
0416

~~2:

.?~22

~~23

.:' 42 4
.: 42 5

z4 2 ~

-:t.27
{432

2.52j
13 76
7 67 6
7 67 6

0414

0417
0420
0421
0422
0423
121424
.042~
0426
0427
0430
0431
0432

,' 5:

: ..; ..
.:0: 2

I
I

670

'c; .

2 63

2063

l4 .52
?433

~ ...

......

"'"

."' J 3~

~3:4

1764
2100
0102
1113el4
0506
1()710
1176
7676

·?
v

...,. 'X

z:22

l4 -i; ~

::~: 5

£436

l:.,

0433

•' .. 3 7

:.:. 76

0434
0435
121436
121437
044121
0441
0442
121443
121444
121445
0446
0447
0450
121451
121452
0453
121454
0455
0456
0457
0460

~~4i

7 0 76

.. ..,.""

-.L

244:

::::. 7 ~

~ 442

7 6 :- 6

~443

242?
2627

6176
7676

,?44 5

3,? 3:

i446

3233
3435

2425
2627
3031
3233
3435

(_ 4,,..(..

.5637

3637

~ .;5:

0:~41.

4ill41

,'4:>2

4243

4243
4445
4647
511151
5253

;'' 4 4

[447
~

.... ..,

..:'~53

4~45

~·454

.; ::i4 7

~455

o; • o;.

L"~56

=-253

... ~..,

:; ~5 5

t..
o;'

.......

r:.c-z:

_:'461
\

"' ,; .....

..... ,.t:_

.... 1.. ....

...L

5455
6621

6 f.2:
... ...,..,f...
I '

::·:,

TAB[,

7676
7676

/ALTMODE-CAS(/4~TMODE-CASE
/RUBOUT-DE~/LEADER-NULL

/N9T USED
IN, U,
IN, U.
/BEL~/N,

lJ,

/TAB/L. >, -"1ET A
IN.

/CR-EOLIN, U,
IN,
/N,
/N,

/N,
IN,

/N,
/N,

U,
U,
U,
U,
U,
U,

/ALTMODE-CASE/N, U,
/N,U,/SPACE•SPACE
/EXC,PT/DBL,QUOTES
/NUMBER SIGN/DOLLAR SIGN/PERCENT-P,C/AMPERSAMD-AMPERSAND
/APOSTROPHE~AP,/OP PAREN
/CL PARD1/*
/PLUS-+/COMMA-,
/MINUS··/PERIOD- •
IS LA SH ·S LA SM ll ER 0-0
/1/2
/3/4
/5/6
1718

/9/N,U,
/SEMICOLON!<
/EQUAL SIGN-:/)
/?/AT SIGN
/AIB
/CID
/E/F
IGIH
!IIJ
/KIL

/MIN
/O/P
/Q/R

/SIT
/U/V

/WIX
I Yli

/LEFT.BRACK/BACK SLASH
/RT.BRACK/UP ARROW
/BACK ARROW/N,U.

121461

'c.-., ~t:

0462

~Je-'

t35t

0463
0464
0465
121466

~46?

6472

'-'46c

0474

fl467

~46 7

6.55b

...

11·,JTIAL START 20
SETuP
.;MP
JMP
I NIT
JMP
GOMAN

::l iZ0,

/INITIAL START 400
JMP
SETUP
J"'P
!NIT

~T400,

/l~!T:ALllE

TRAF PROCESSOR

~
' ,

121274
121275
0276
0277
030121
0301
0302
0303
0304
0305
121306
0307
03Hl
121311
0312
0313
0314
0315
0316
0317
0320
0321
0322

0323
0324
0325
0326

0327
033121
0331
0332
0333

0334
0335
0336

0337
0340

0310
0311
0312

04?1

2313

122;;
i'.: 2 3
4242
6221

;; 314

:'.'31'.5

0316

APO
CLR
STC

0011
4252

121344
121345
0346
0347

/SAVE !T FOR USE AFTER
/CASE C~ARACTER IS OUTPUT
/GET CASE CHARACTER

S TC

,,IMP

REi

/STORE FOR
/EXIT

L.DA

IL8~ER

2317
<i32 0

1120
0055

0321

Ql451

0322
['.;323

Z011

~'32 4

0325
0326
D327
0330
0331
0-532
i 1 333
0334
03-55
0-536

4242
4252
0502

L.Sri,

TRA~SFER

CASE CHARACTERS
ADA I

L:JO,

APO
CLR
STC
STC
!OB
KRBA

102f_1

JMP
SAE
215
JMP
LOA

0212

212

6350

JMP
JMP

6350
1460

/MAKE IT

Ll~C

CODE

6036
L001,

0215
6221

6221

AC
UPC·

/STORE IT FOR TRANSFER
/CLEAR LEFT OVER BUFFER

/READ CHAR AND
/CLEAR KEYBOARD FLAG
/ECHO
IC, R,?

RET

/NO, EXIT
/YES, THROW IN
/A FREE LINE FEED

PR INT
RET

/ILLEGAL CHARACTER
RETX,
LDA I /PRINT UP ARROW

0337
0340

1020
0336

336

l13 41

635;:>

0342
0343

050Zi

JMP
!OB
KR BA
JMP
COM
ROL I

JMP

6036
6352

0344
0345
0346

0017

0347

6255

e261

/ECHO OFFENDING
/CHA RA CTER,

PRINT
/SET LINK BIT
/TO KEYBOARD "PAUSE" VALUE

0302

0350
0351
0352

4 351
43::>2
4353

6046

0353
0354
0355
121356

4354

5.552
6141

v,355

6000

03::>o

i-h;tl

i· 3? 7
l0 3 6 l-'

4252

0361

tEROES

te350

0357
0360

~!NUS

UPC

0341

0342
0343

/DELETE

6041

/PRINT A CHARACTER
/ENTER W ASCII CHAR IN AC
PK!NT, PDP
PM ODE
TLS
TSF
JMP
.-1
LI NC
LMOOE
JMP
0
/IN!T!AL!2E THE TRAP PROCESSOR
!\JlT•

~)~~ ~~ 1

CLR

STC
AXO

lJPC

/CLEAR LEFT OVER CHARACTER
/BOILER PLATING FOR GUIDE
/RESTART
/GET SPEC, F~S. REG,
/SET TRAP ENABLE BIT

0362
121363

<1361

0C24

0364
0365

cl.56 2
0363

1622
1000

10iiHc

0366
121367
0370
0371
-:~-.~~,2

0.364

065

0004
6000

ESF
JMP

/READ IT BACK OUT
/RETURN
~

040121

6025

JMP

RST401ZJ

!GO TO START 400 ..,./

SFA
BSE
ENOX,
*40~

/CONTROL ROUTINE

., ' ,
""II

"'\'i;;:;

<'Ii 7 0

Z177
3202

eiu:

n
--

c122 4
;\~);.:;
£; c .. ,.,
:: 22 t

Z2 27
z 2 30

Hl20
000
J321
..1

0043
0017

0202

~231

1020

0203
0204
0205
0206
0207

2232

0000

Z2..53

~314

0210
0211
0212
0213

0214
0215

0216
0217
0220

0221
0222
0223
<7224

0225
0226
0227

02..56
l24:!.
:{242
i'2 43
22 44
2245
0240
0247

05 00
6244
0000

3777

J25i

<:1325

(1262

0263
0264
0265
0266
026 7

1020
00 00
0450

RTJ

STC
A 'JA

AC,

RTJ,
OVN,

0
DJR

/RESTORE AC
IINH!B!T tERO CLOBBERING
/IN USERS MEMORY SEGMENT
/RESTORE INTERRUpT BUFFER
/BECOMES JMP TO USER PROG,

IO B
RMFA
HLT
3777

/K8D PROCESSING
5
DOK8D, RQR

/PUT TRAPPED l~STRUCTION
BIT INTO COMPUTER
/LINC BIT
/GET LEFTOVER CHAR,
I IF ANY
/LEFTOVER CHARACTER?
/YES. DELI VER IT T 0 USER
/NO, FRESH CHARACTER?
/YES, GO READ IT
/NO, PAUSE?
/YES, HANG IN THERE
/TILL KEY STRUCK,
/NO, RETURN TO USER W. AC
/CLEARED

UPC,

LP,

LOA
0
AtE
JMP
KST
JMP

LOO
GRC

LtE

JMP

LOO

0262
<1263
0264
J265
C266
J267
?27 a
0271

l272
2273
Z274
2275

0011
2\5>')0

6034
1120
7602
033'1

/READ AND TRANSLATE
GRC,
CLR
!OB
KRSA
ADA
-175

ROR
8CL

1560

4276
1300

ADA
TAB
STC
LOH

04~11

;12 76
,_. . 2 r 7

2ll" e'>0

1420

SHO

...

76,t."",0

7600

"~ S;c' 1

6.537

JMP

<.)3 ;!2

112 ,)
7722

ADA

-... V

0303
0304
<J305

A ~EYBOARQ

CHARACTER

/READ A CHARACTER
/CALCULATE CHARACTER CON/VERS! ON TABLE INDEX IN
/HALF WORDS

37021

3700
1120

/ADD BASE ADDRESS OF TABLE
• +2

/HALF-WORD PICKUP ADDRESS
/GET TYE LINC CHARACTER,
/JS

IT AN UNDEFINABLE?

RE.TX

/YES. ECHO UPARROW
/IS IT UPPER CASE?

LOW

/NO,

.55

APO
JMP

0451
6.517
I

02713

0271
0272

BSE
JMP

/LOADS Q REGISTER
/FROM AC
/OBTAIN ADDRESS FOR RETURN
/TO USER PROGRAM

6323

0254
0255
0256
0257
026<?
0261

2261

Ql251
0252
0253

ROR
LJA

0241
21242

0246
0247
0250

Cl '

LINK~

/RESTORE
/RESTORE LOCATfON 0
/RESTCRE Q REGISTER

Li) A
0

140

2l236

0245

l~Z(J

0237
0242
0243
0244

SET
17

014<'1
1620
6000
42 46
1120
0000
J006

6323
0435
6262
0452
6255

0235

22.S4

2251
02 52
2253
254
2255
0256
2257
2260

02 30
0231
0232
21233
0234

2
K 8R

~235

'l 2 3 7
J2 40

/GET LINK

L.. DA

LC'

/ITS AN UPPER CASE CHARACTER
0306
ri 7

.~..,

1120

ADA

{):r?I o4 1

/MAKE IT LINC CODE

'O 'IJ f 0

012177
010121
011211
121102
12111213
011214
0105
121106
0107
121110
0111
0112
0113
0114
0115
121116
0117
0120
0121
0122
0123
0124
0125
0126
0127
0130
0131
0132
0133
0134
0135
0136
0137
0140
0141
0142
0143
0144
IH45
0146
0147
0150
0151
11.115 2

r1J153
0154
0155
0156
0157
0160
0161
0162
0163
121164
0165
0166
121167
0170
121171
0172
0173
0174

~~';;.:....iii-~...
~:.;.;..
~

/TRAP ENTRY AND MACHINE STATE SAVING
•141
0141
e142
'11143

0144
0145

4242
0261

4225
0005
0241
0455
2136
4232

0146
0147
015e
0151
0152
0153

0011

0154
0155

4222
0057'

0156

0000

STC
ROL
STC
QAC
ROL

AC
1

LC
1

QL. i!

ADD
ONE
STC
Q
ADD ONE
FLO
CLR
STC
OVL
SET
17

2136

0454

/SAVE AC
/SAVE L!Nt<
/GET H 0 11 Q REG BITS
/GET L 0 BIT
/SAVE IT
/GET OVERFLOW BIT IF ON
/SAVE !T,0=0FF, 1=0N
/SAVE LOCATION 0

0
I

0157

0002

4160
4161
4162
4163
4164

0234
0335
1371
3364
74'12
7240
1140
3334
1734

4165
4166
4167

4170
4171

4172
0173

0174

0175
0176
0177
0200
0201
0202
0203
0204
0205
0206
0207
0210
0211
0212
0213
0214
0215
0216
0217
0220

0201
6141
1460
0515
0467
0250
1460

0535
ii'467
6250
1460
0534
0467
6212
1460
0514
6130
1000
0242
05N.'

61:146

/INSTRUCTION IDENTIFICATION.
PDP
PMOOE
/READ I~TERRUPT BUFFER
FETCH, RIB
/GET INSTRUCTION FIELD
M7VI
AND
/MAKE IT INTO A CDF N
CDFX
TAD
,+1
DCA
/BECOMES CDF N
7402
/SET AC TO •1
STA
/COMPUTE ADDRESS OF
140
TAD
/TRAPPED INSTRUCTION
PC
DCA
/OBTAIN INSTRUCTION
PC
TAO
/CAUSING TRAP
/SET DATA FIELD TO 0
COFX,
COF
LINC
LMODE
/IS IT KBD?
SAE I
KBD
/NO
SKP
/VES,
OOKBD
JMP
/IS IT KBD I?
SAE
KBD
/NO,
SKP
/YES,
DOKBD
JMP
/OPR I 14?
SAE
QPR
14
/NO
SKP
/YES
OP14
JMP
/OPR 14?
SAE
QPR
14
/PUT JMP TO
ERR
OTHERS, JMP
/CHECKS FOR OTHER
/INSTRUCTIONS HERE,
/OUTPUT, GET CHARACTER
OP14,
LOA
AC
IOB
/OUTPUT IT
TLS4
108

0500

TSF'A
JMP

6041
6216

/CHECK IF DONE
,-2

"'21
""'222
0223

1020

0000
2247

/RETURN TO USER PROGRAM
/EXIT TRAP PROC~R
RET,
L.DA I

ovi.,
ADD

OVN

/3777 CAUSES av

0300
0001
0002
0003
0004
0005
0el06
0007
0010
0011
0012
0013
0014
0015
0016
0 01 7
0020
0021
0022
0023
0024
0025
0026
0027
0030
0031
0032
0033
0034
0035
0036
0037
0040
0041
0042
0043
0044
0045
H46
0047
0050
0051
0052
0053
0054
0055
0056
0057
0060
0061
0062
0063
0064
0065
0066

<>2l
1~ ! 'vC-8 s p10:.. ATCR TRAP PROCESSOR,

1:0P•Rl~~T
/~AY\A~C,

0074
0075

(

EQUIPMENT CORP,

OlGITAL

'1ASS.

/J,

LA\~Btl~,

~AY

1969

/REvlSEJ 2~ Ju~Y 190~
/REV!SEJ 8 AUGUST 1969
I

/OPERAT!J\ 8EF"l\!T!O~S rOR LINC MODE ASSEMBLY
/OF' PDP•8 MODE !OT lNSTRUC!ONS
KCCA:6032
KRS060.34

KR806036
TSF"A:;;6i/J41
TLSA:;6046
RMF' A=6244

/SOME LINC·8 DE•INITIONS
OPR=500
KBD=51?

•2;?!

0020
0021

6463

JMP

ST20

0o43

LDF"

3
2

k::rt'12

0602

ur:

0023

0006
0020

JMP

0024

OJR

/BECOMES JMP INIT

/GO TO 20 IN SEGMENT 2
/(04020)

/4'1li2l RESTART
RST400, JMP
L.Dr

tHl27

0466
0643
0602

0030

0~06

DJR

00·51

012!00
b400

HLT

0025
0026

11rn32

Llf'

JMP

ST400

/BECOMES JMP INIT

3
2
400

/GO TO 400 IN SEGMENT 2
I (04400 l

0033 . 6356
0034 0642
0'135 0 /11!0
7400
00:S6
0037 0643
0040 0602
0041 7400

/START GUIDE
JMP
GU IDE,
LDr
RDC

I NIT
2

7400

LDF'
Llr
JMP

3
2
140~

/READ GUIDE START BLOCK
/INTO QUARTER 3,SEGMENT 2
/START GUIDE

/ERROR STOP
•130
0130
01.H

.H:l012l

ERR,

6221

Hi.T
JMP

RET

/UNIDENTIFIED INSTRUCTION
/IN AC AT HLT. RETURNS TQ
/USER w AC CLEARED WHEN
!CONTINUE PRESSED,

0067

0070
0071
l'l072
011173

:969,

OE~-s llB.

/~ISC

CONSTANTS

•134

0134

0000

PC,

0135
0136

0070
0001

M?0,

ONE,

/ADDRESS Of TRAPPED
/INSTRUCTION