23 January 2024, 21:09 | #1 |
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VASM and BKPT
Hello it's me again with a VASM (or better said assembly question)
If I take a look into the MC68000 manual I see a mnemonic called BKPT. In the manual it is said that this is for MC68EC000, MC68010, MC68020, MC68030, MC68040, CPU32. When I try to assemble with VASM: Code:
BKPT #7 Code:
error 9 in line 1 of "test.s": instruction not supported on selected architecture > bkpt #7 Then I made a quick test: I put all the bits described in the m68k manual by hand for "BKPT #7" which gave me opcode $484F. Bits: Code:
0100100001001111 => $484F Code:
PEA A7 Last edited by fuzzylogic; 23 January 2024 at 21:10. Reason: typo |
23 January 2024, 21:24 | #2 |
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I never heard about bkpt instruction. Perhaps pea is correct name.
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23 January 2024, 21:40 | #3 | ||
Natteravn
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Quote:
EDIT: Checked the whole PRM, but BKPT remains the only instruction which differs between 68000 and 68ec000 (if this is not a bug in the Rev.1 M68000PM/AD. Move from SR is supervisor-only on 68ec000, but this makes not differences for the assembler. Interesting. Didn't know about BKPT on 68ec000. Try to assemble for 68010 and bkptwill work. Quote:
Last edited by phx; 23 January 2024 at 21:51. Reason: Some investigation. |
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24 January 2024, 08:02 | #4 |
son of 68k
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Unless you are using special hardware that can catch the breakpoint acknowledge bus cycle (which is different between 68010 and 68020, missing in 68000 and perhaps again different in 68040+), bkpt does nothing but trigger an illegal opcode exception. So in some way, it works for 68000 too.
At least Devpac3 assembles it even in 68000 mode (phxass needs 68010). |
24 January 2024, 17:03 | #5 |
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Thanks guys for the clarification. I have never seen this before and was wondering.
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25 January 2024, 01:25 | #6 |
Natteravn
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Does anybody know if the 68ec000 does a breakpoint acknowledge bus cycle? I would expect that. Otherwise there is no reason to document that the
bkptinstruction is available on the 68ec000, but not on the 68000. And is there a difference between the 68ec000 and the 68sec000? I have the latter in my Minimig and could do some tests. |
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