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DEC-08-LRAA-D

December 1965

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Document:	dec-08-lraa-d
Order Number:	DEC-08-LRAA-D
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Pages:	8
Original Filename:	https://svn.so-much-stuff.com/svn/trunk/pdp8/src/dec/dec-08-lra/dec-08-lraa-d.pdf

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IDENTIFICATION
Product Code:

DEC-OS-LRAA-D

Product Name:

Reod—In—Mode Loader

Dore Created:

February 23, I965

Maintainer:

Software Services Group

FOP-B
Ll-HARY

DEC—08-LRAA-D

ABSTRACT

The Rim Loader is a minimum-sized routine for reading and storing information contained in
Read—In—Mode coded tapes via the ASR—33 perforated tape reader.

REQUIREMENTS

2.l

Storage
17 decimal

2.2

(21 octal).

Equipment
4K PDP-8 with ASR—33.

USAGE

3.l

Loading
To place the Rim Loader into memory via the control console switches,

3.l .l

Set 7756 in the switch register

3.1.2

Press LOAD ADDRESS.

3.1.3

Set the first instruction

3.l .4

Press DEPOSIT.

3.l .5

Set the next instruction

3.1.6

Press DEPOSIT.

3.l .7

Repeat steps 3.1.5 and 3.l .6 until all

3.2

Calling Sequence
None.

proceed as follows:

(SR).

(6032) in the SR.

(603i) in the SR.

instructions have been deposited.

Cannot be called as a subroutine.

DEC—OS-LRAA—D

3.3

Start-up/Entry

3.3.l

Place the perforated tape which must be in RIM format in the perforated—tape reader.

3.3.2

Make sure that the ASR-33 is on line.

3.3.3

Place the starting address 7756 in the switch register

3.3.4

Press the LOAD ADDRESS key.

3.3.5

Press console START key.

3.3.6

Move the reader control switch to START.

3 .4

Errors

There are no error stops in this routine.

DESCRIPTION

This is a basic routine that alternately assembles an addr (:35 from two successive characters on

tape, then assembles data contained in the next two characters and stores this data at the associated ad-

dress.
Because a tape in Rim format is twice as long as a comparable tape in

Binary format, it is

suggested that the Rim Loader only be used to read in the Binary Loader. After this, the Binary Loader
should be used.

FORMAT

5.1

External Data

Tapes to be read by this program must be in Read-In-Mode coded format.

5.] .l

Leader should be about 2 feet of Leader—Trailer codes (any code with channel 8 punched;

preferably code 200).

5.1.] .l

Depress ALT MODE, CTRL, and @ keys simultaneously to punch 200 Leader—Trailer.

5.1 .2

Characters representing the absolute, machine language program are arranged in an alternat-

ing pattern of address, contents, address, contents, etc. Addresses have channel 7 punched, channel 8
not

punched. Contents have no punch in channel 7 or 8.

5.1.3

Trailer:

5.] .4

Example of Read—In-Mode coded format:

Same as Leader.

Tape Channel
Channels 8 and 7 Indicate.

87 654 S 321
10 000
01 Al
00 A3
00 D1
00 D3

000

‘Leader code is always found first.

Absolute octal Address of data in next two characters.

Octal Data to be stored at preceeding address.

D2
D4

This pattern repeats in similar four character groups until the concluding
10 000

5.l .4.l

Trailer Code is encountered.

000

Note that actually a 3-bit group (a single octal

character) is designated by the notation Al

The ”l" in this notation indicates that this particular octal character will be used as the most

above.

significant three bits in specifying the absolute address into which following data will be deposited.

Correspondingly, A2, A3, and A4 designate successively less significant octal characters in the absolute
address

5.l .4.2

The remarks in 5.1.4.1

apply equally to Data as specified by the notation D1, D2, D3, and

D4.

PROGRAM

6.l

Program Listing

Abs.

Octal

Addr.

Contents

Instruction I Z

Tag

Comments

7756,
7757,

6032

KSF

/clear AC and flag
/sl<ip if flag l

JMP .-l

/looking for char

KRB

/read buffer

KCC

BEG,
'

603i

7760,

5357

776i I

6036

‘

AAsijr'

C212?“

7762,
7763,
7764,
7765,
7766,
7767,
7770,
7771,
7772,
7773,
7774,
7775,
7776,
7777,

7106

CLL RTL

7006

RTL

7510

SPA

Instruction I Z

Tag

5357

JMP BEG +1

7006

RTL

6031

KSF

5367

JMP .-1

Comments

/ch8 in ACO
/checking for leader
/found leader
/OK, ch7 in link
/read, do not clear
/checl<ing for address
/store contents
/store address
/next word
/temp storage

KRS

6034
7420

SNL

DCA I TEMP

3776
3376

DCA TEMP

5356

JMP BEG

TEMP,

JMP start of bin loader

ADDENDA

7.1

Other Possible RIM Loaders

Variations of the RIM Loader described may prove useful in special

cases

where, due to cir-

cumstances, RIM must be located in a different section of core.
On the other hand, the equipment involved may make it necessary to use a variation of RIM

tailored specifically to a particular situation.
PDP-8 system used for text editing.

As an example of this, consider a special—purpose

In this system,

ASR-33's are used.

Instead several typewriters

which use a different code (including provision for upper and lower case) are time-shared with respect
to

input and output with a central PDP-8.
Please consult the Applied Programming Department at Digital

Equipment Corporation for de-

tailes of other RIM Loaders currently available or for assistance in special cases.

7.2

The Use of PDP-8 System Programs
Certain system programs such

RIM Loader precisely

7.3

the DECtape Library System (Digital—8-8-5) require that the

listed above (6.1) be used.

Using the RIM Loader with an Extended Memory
The RIM Loader as described and‘listed up to this point may

actually run in any memory field

provided that it is loaded into memory following a slightly different procedure than that described in 3.1
above.
to

The Instruction Field register and the Data Field register must both be set to N (a number from 0

7) where

N indicates the memory field in which the RIM Loader is to be placed.

This is easily done.

/\
V/

7.3.]

Set the data field extension of the switch register to N.

7.3.2

Set the instruction Field extension of the switch register to N.

7.3.3

Follow procedure in steps 3.1.]

through 3.1.7 above.