PDP-8 diagnostic tests

Scott Baker scott.l.baker at gmail.com
Tue Aug 23 14:31:42 CDT 2016


I have written a PDP-8 VHDL model and I have it running in an FPGA

At this time it has passed a basic DEC diagnostic instruction test but
I found some interesting things when getting that instruction test to pass.
For example:

The following segment of code implies that IAC instruction affects the Link

 1797             /GROUP 1 OPERATE TEST 33
 1798 02626 7300          CLA CLL         /AC=0000 LINK=0
 1799 02627 1053          TAD K2525               /AC=2525
 1800 02630 7261          CLA CMA CML IAC /TEST COMBINATION
 1801 02631 7420          SNL
 1802 02632 7430          SZL
 1803 02633 7402          HLT             /CLA CMA CML IAC FAILED, AC SHOULD
 1804                                     /BE 0000, LINK SHOULD BE ZERO

but the PDP-8 Handbook  ; DEC copyright 1966; page 14
says nothing about the Link bit being affected by the IAC instruction.

The simh PDP-8 simulator also shows that L is affected by IAC.

If I change this test line from

 1800 02630 7261          CLA CMA CML IAC /TEST COMBINATION  << link=0


 1800 02630 7261          CLA CMA CML  /TEST COMBINATION  << link=1

Can anyone point me to:

1) DEC documentation which more fully describes all the instruction set (in
more detail  than the PDP-8 handbook)

2) Some more instruction tests in assembler source code format. I have
found lots of binary files but I would prefer assembler source code format.
I am using a pal compatible cross assembler.

Thanks and Regards,

More information about the cctalk mailing list