Subject:
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hforth register usage
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Newsgroups:
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lugnet.robotics.rcx.pbforth
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Date:
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Fri, 19 May 2000 02:31:54 GMT
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Reply-To:
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sjm@judgement.com{nomorespam}
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Viewed:
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1085 times
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Ralph,
I'm trying to add an assembler word and trying to deduce register.
usage. Could you verify for me please.
It looks like the top cell on the stack is actually a register (r6).
The second cell on the stack is pointer to by r7.
This means that consuming a stack cell means using the value in r6
and when done pop a new value into r6 from the data stack. Similarly
pushing a new value on the stack means first pushing r6 on the stack
and putting the new value in r6. A word consumes one value from
the stack and then pushes a new one just reads the old value from r6
sets r6 to the new valuewithout touching the stack pointer.
r5 is the return stack pointer. I have no need to touch this.
r4 is the next word pointer. I have no need to touch this.
r3-r0 seem to be available as scratch registers to assembler code.
Of course all of these registers have appropriate mnemonics.
Am I close?
Steve
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Message has 1 Reply:
 | | RE: hforth register usage
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| (...) Right. If you look at the beginning of h8hforth.asm, I've abstracted the actual register names so I could move them around....here's the snippet from the file... ; The H8/300 Forth machine register usage has to be closely intertwined with ; (...) (24 years ago, 19-May-00, to lugnet.robotics.rcx.pbforth)
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