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PDPjs passes the first four PDP-10 Basic Instruction Diagnostics (finally)

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Jeff 2017-03-27 19:00:10 -07:00 • committed by Jeff Parsons
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_posts/2017-03-24-stepping-through-pdp-10-diagnostics.md
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@ -59,7 +59,9 @@ Happily, this was a good outcome, because 035057 is the end of the test. If you
035057 254 00 0 00 030057 ENDXX: JRST BEGEND ;LOOP PROGRAM
Next, I tried [KA10 Basic Instruction Diagnostic #4 (MAINDEC-10-DAKAD-B-D)](/apps/pdp10/diags/klad/dakad/):
I had similar success with Basic Instruction Diagnostics #2 (MAINDEC-10-DAKAB-B-D) and #3 (MAINDEC-10-DAKAC-B-D).
However, when I tried [KA10 Basic Instruction Diagnostic #4 (MAINDEC-10-DAKAD-B-D)](/apps/pdp10/diags/klad/dakad/):
>> a 30724 /apps/pdp10/diags/klad/dakad/DAKAD.MAC
starting PCjs MACRO-10 Mini-Assembler...
@ -177,8 +179,27 @@ not WORD_MASK, to truncate the value to 36 bits. Here's the corrected line:
var dst = (this.readWord(acc) + 0o000001000001) % PDP10.WORD_LIMIT;
```
There are more PDPjs emulation failures in these [Basic Instruction Diagnostics](/apps/pdp10/diags/klad/) from DEC,
but I've run out of time today. To be continued....
The next problem I encountered involved this instruction in DEC's "DAKAC" diagnostic:
CAME [0,-1] ;PASS TEST IF C(AC)=0,,-1
Based on the comment, it's clear what they really meant was either "[0,,-1]" or "[XWD 0,-1]". However, they still got the
desired result, which means that even when the assembler parses an mnemonic-less instruction like "0,-1", it must still truncate
the second (address) operand.
The last few problems I ran into during my initial testing were in DEC's "DAKAD" diagnostic. When it tests the `SOJ` and `SOS`
instructions, it expects the carry and overflow flags to be set consistently with an *addition* of negative 1 (777777,777777)
rather than a *subtraction* of positive 1. That was an easy fix, but I'm not convinced that all flag-related issues are resolved,
so more arithmetic operation testing will be performed at a later date.
Finally, when the "DAKAD" diagnostic generated an indirect word reference:
E217: E217A(3)
my MACRO-10 Mini-Assembler passed the reference to the Debugger's assembler function first, because that function already knows
how to parse address expressions that use indirection and/or indexing, including expressions (eg, "E217A") that require a fix-up.
Unfortunately, the Debugger failed to pass the fix-up information back to the MACRO-10 Mini-Assembler, because evaluation of the
indexing expression was overwriting fix-up information, if any, from the preceding expression.
*[@jeffpar](http://twitter.com/jeffpar)*
*Mar 24, 2017*