Digital PDFs

DIGITAL-8-18-U

December 1967

8 pages

Original

0.3MB

Document:	digital-8-18-u-d
Order Number:	DIGITAL-8-18-U
Revision:
Pages:	8
Original Filename:	https://svn.so-much-stuff.com/svn/trunk/pdp8/src/dec/digital-8-18-u/digital-8-18-u-d.pdf

OCR Text

IDENTIFICATION

PRODUCT CODE:

Digital-8—I8—U-Sym

PRODUCT NAME:

Alphanumeric Message Typeouf

DATE CREATED:

February 16, I967

MAINTAINER:

Software Service Group

POP-8
LIBRARY

Digital-8-l8— U-Sym

ABSTRACT

A basic subroutine to type messages packed in computer words.

packed internally in a single word.
243 and 245) can be typed.

Two 6-bit characters are

All ASR—33 codes from 30] to 337 and from 240 to 277 (excepting

The typing of line-feed (code 2l2) and carriage-return

possible by arbitrarily assigning internal codes of 43 and 45,

respectively,

thus preventing the output of ASCII codes 243 (#) and 245 (%)

(code 215) are made

represent these characters,

REQUIREMENTS

Storage
This subroutine occupies 48 (decimal) storage locations in core plus autoindex register l0

(octal)

page 0.

Equipment
Basic PDP-8
3

USAGE

3 .l

Loading
This subroutine may be placed in memory by the use of the Binary Loader.

supplied
3.2

The

library tape

is symbolic.

Calling Sequence
The calling sequence is designed so that the user may easily incorporate messages in his pro-

gram.

The tollowing example illustrates a simple usage of this program.

/TEST 8-18-U
/START ADDRESS IS 400
/PRINTS AB HI E.R. Dow AND HALTS AT LOC. 407
*400
/ORIGIN AT 400
JMS
START,
IADDR/ JMS To MESSAGE SUBR
0102
/AB
1011
/HI
0556
/E.
2255
/R.
0417
/Do
2700
/W+ END CHAR
HLT
END,
/END OF PROGRAM
MESSAGE
ADDR,
/ADDRESS OF MESSAGE TYPEOUT SUBROUTINE
4.

RESTRICTIONS

The end—of—message code consists of

008

(0000002), of course, only

end-of—message

code may appear in the most significant six bits of location at the end of the message if the message
consists of an even number of characters.

Digital—8-I8-U-Sym
5.

DESCRIPTION

The ASCII code breaks down into two main groups:

first, the set of codes from 30I to 337

inclusive; and second, the set of codes From 240 to 277 inclusive. Combined, these two sets represent
63 characters. It is not necessary to store the most significant octal digit of the code For these characters,
2 or 3, internally since it may be computed from a knowledge of the least two significant digits, in other
words From a "stripped" code.
Codes 3XX where digits XX are greater than 37 and codes 2XX where XX is less than 40 do
this scheme and must be handled by special means.

Only two such codes are necessary to ac(code 2l5)
which are assigned "stripped” code representations of 43 and 45, respectively, making the actual codes
243 (#) and 245 (%) illegal for this subroutine; e.g., when an internal code of 43 is found, it is discarded
not fit into

complish the purposes of this subroutine.

These are line-Feed (code 2I2) and carriage-return

and a 2I2 is sent to the ASR-33.

Section 7 contains a complete table of internal and external codes legal and illegal for this

subroutine.
METHOD

Upon entry MESAGE will hold the address of the First message word. One is subtracted
The main loop is then entered.

from this and the result deposited in autoindex register I0.

The message word is deposited in MSRGHT, then rotated six bits to the right. A iump to the
minor subroutine TYPECH causes the character now contained in the six least significant bits of C(AC) to

be typed.

A second jump to TYPECH causes the character contained in the least significant six bits of

MSRGHT to be typed.
If at any time TYPECH Finds the least significant six bits of its current data word to be 0

(the end-of—message code), MESAGE will return to the calling program.
After each two passes through TYPECH
next message word is

main

picked up by

(if an end-of-message code is not encountered), the

indirect TAD instruction referencing location 00I0 (octal) and the

loop repeats.
FORMAT

For this program external

(ASCII) and internal core Formats may best be illustrated by the
‘

following tables.

LE GAL CHARACTERS
Internal

Internal

(Stripped)

ASCII

Character

301

302

ASCII

Character

312

3T 3

303

3l4

304

3T5

305

3l 6

(Stripped)
'

306

3T 7

307

320

310

32I

I I

3T I

322

Digital—8-I8-U-Sym

LE GAL CHARACTERS

Internal

(continued)
Internal

(Stripped)

ASCII

Character

(S tripped)

ASCII

323

252

324

253

325

254

326

255

327

256

330

257

33I

260

332

26I

333

262

334

263

335

264

Character

,
-

336

265

337

266

240

space

267

24I

270

242

”

27I

243

line feed

272

244

273

;

245

$
carriage return

274

246

275

247

76'

276

250

277

25I

(
)

Illegal codes, that is codes that will never be sent to the ASR-33 by this subroutine, are
The characters represented by these ASCII codes cannot be typed by this sub-

shown in the next table.
routine

ILLEGAL CODES
ASCII

Character

300

374

ACK

375

ALT MODE

377

RUB OUT

204

EOT

205

W RU

206

207

BELL

243

245

Reason for

Illegality

Stripped code 00 needed for end-of-message code
Greater than 37 internally
Greater than 37 internally
Greater than 37 internally
Less than 40 internally
Less than 40 internally
Less than 40 internally
Less than 40 internally
Arbitrarily used in stripped form for FORM FEED
Arbitrarily used in stripped Form For CAR. RETURN

Digital-8-l8- U-Sym

Note that there are only ten illegal codes.

The illegal codes are not frequently necessary

Furthermore, in cases where they might be useful they can be represented by
of
combinations
legal characters. For example @ may be represented by ”AT" while # may comsimple
monly be represented by ”NO."
in alphanumeric messages.

EXECUTION TIME

This subroutine is output limited.
PROGRAM LISTING

/DIGITAL 8-18- U
/MESSAGE TYPE-OUT
/CALL WITH A JMS MESAGE
/WITH DATA FOLLOWING
/RETURN FOLLOWING END OF MESSAGE
/CODE(DO)
@299
$261
@292
@205
02D4
6285

@639

MESAGE,

724D
120D
561%
1416
5216
1216

CLA
TAD
DCA
TAD
DCA
TAD

D267
D219
D211
@212
6215
6214
@215
9216

7912
7012
7012
4217
1216
4217

RTR
RTR
RTR
JMS
TAD
JMS
JMP

@217
D22D
D221
D222
D225
D224
D225
D226

DEED
0250

D206

52fl4
DDOO

745%
5413
1251
759%
5238
1252

D227
D25D
D251

5243

2252
2253

5235
1254
5245
1255
7443
5242
1256
5245

D254
D235
D256
D237
D24D
D241

1255
7440

MSRGHT,
TYPECH,

CMA
MESAGE
16
I 1%
MSRGHT
MSRGHT

/SET C(AC):-1
/ADD LOCATION
/AUTO-INDEX REGISTER
/FETCH FIRST WORD
/SAVE IT

/ROTATE 6

TYPECH

/TYPE

MSRGHT

/GET

BITS

RIGHT

DATA AGAIN
/TYPE RIGHT HALF
/CONTINUE
/TEMPORARY STORAGE

/TYPE

TYPECH
MESAGE+4

AND MASK77
SNA
JMP I 1%
TAD M4D
SMA
JMP .+3
TAD C549

JMP
TAD
SZA
JMP
TAD
JMP
TAD
SZA
JMP
TAD
JMP

MTP
M5
.+3
C212
MTP
M2
.+5
C215
MTP

CHARACTER

C(AC)6-11

/IS IT END OF MESSAGE?
/YES: EXIT
/SUBTRACT 4B
/<4D?
/NO
/YES: ADD 53%
/TO CODES <49
/SUBTRACT 5
/IS IT ZERO?
/NO
/YES: CODE 45 IS
/LINE-FEED (212)
/SUBTRACT 2
/IS IT ZERO?
/NO
/YES: CODE 45 IS
/CARRIAGE-RETURN (215)

Digital—8—18-U-Sym

C242

1257

C245
2244
C245

6246

4246
2247

7252
5617

C252
2251

2277
7742

0252

2342

C255
2254
2255
2256
C257

7775
14212
7776
C215
@245

MTP,

6C41
5244

TAD

C245

TLS
TSF
JMP
CLA
JMP

.-1

TYPECH

/ADD 222 TO OTHERS >43
/TRANSMIT CHARACTER
/wAIT FOR FLAG
/NOT SET YET
/SET: CLEAR C(AC)
/RETURN

/CONSTANTS

C212

C256

C245
C542

C257

54%
-5
212
-2
215
245

2252
B259
921MB
9216
@245
@3255
13255

TYPECH

(6251
{15217

10.

REFERENCES

M412)

77
~42

C254

C215

MASK'I?
MESSAGE
MSR GHT
MTP
M2
MS

MASK77,
M42,
C543,
M5,
C212,
M2,
C215,
C245,

Digital-8-I9-U (Teletype Output Subroutines) and Digital-8-20-U (Character String Typeout).