Saturday, February 8, 2014

Testing the 4510 CPU

As mentioned previously, I am now working on extending the C64 Emulator Test Suite to create a C65 emulator test suite.  In the first instance, this is all about testing coverage of the extra 4510 operations.

The existing tests in the C64 Emulator Test Suite are good, but the assembly code for them is poorly documented, and being written using Turbo Assembler on a real C64, they are 95% shared code.

I have tried to improve this situation by factoring out a lot of the common parts of the tests, and using the .include directive of Ophis, so that a complete test is <100 lines, and each of the includes and parts of the test itself are fairly well documented.

For example, the test for PLZ is:

  .include "test_top.a65"

         .byte 145,"PLZN"

  .include "test_prepare.a65"

         ; perform one test
next:     ; expect data byte to be in results
         lda db
         sta dr

         ; expect Z and data byte should be identical
  lda db
         sta zr

         ; expect A to be the same in the results
         lda ab
         sta ar

         ; expect x to be the same in the results
         lda xb
         sta xr

         ; expect Y to be the same in the results
         lda yb
         sta yr

         ; expect processor flags to have B flag set and E flag set
         lda pb
         ora #110000
  and #%01111101
         tax
         lda dr
         cmp #0
         bne nozero
         txa
         ora #000010
         tax
         lda dr
nozero:  asl
         bcc noneg
         txa
         ora #%10000000
         tax
noneg:   stx pr

         ; expect SP to be one more than it started
  ; but in practice, the value will be the same, because we will be pulling
  ; a byte off that we have pushed
         ldx sb
         txs
         stx sr

  ; push data byte onto stack to be pulled off by the instruction
  lda db
  pha  

  .include "test_setup.a65"

         ; test instruction
cmd:     plz

  .include "test_record.a65"

  ; for stack pull instructions, data value is the appropriate register
  lda za
         sta da

  .include "test_check.a65"

  ; name of next test
name:    .byte "PHWIL"

  .include "test_common.a65"

I am sure there will be further changes before it is all done and dusted, but I can now fairly rapidly write tests for the simpler instructions.

Those interested can check out http://github.com/gardners/4510tests

If anyone with a real C65 is willing to run the tests on their machine in C64 mode, that would be a great help to verify that the behaviour I am implementing is correct.  I can provide a D81 file of the current set of tests if anyone is able to help out.

No comments:

Post a Comment