45 lines
649 B
ArmAsm
45 lines
649 B
ArmAsm
.define .exg
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.sect .text
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.sect .rom
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.sect .data
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.sect .bss
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.sect .text
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! Exchange top bytes of stack
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! Expects in de-registers the number of bytes to be exchanged.
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.exg: mov a,e
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rar
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cc eoddz !trap if numer of bytes is odd
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pop h
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shld .retadr
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mov h,b
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mov l,c
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shld .bcreg
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lxi h,0
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dad sp
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mov b,h
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mov c,l !now bc points to first operand
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dad d !and hl to the second
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push d !place number of bytes on top of stack
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1: mov d,m
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ldax b
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mov m,a
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mov a,d
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stax b
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xthl !caused by a lack of registers
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dcx h !decrement top of stack
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mov a,h
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ora l
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xthl
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inx h
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inx b
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jnz 1b
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pop d
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lhld .bcreg
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mov b,h
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mov c,l
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lhld .retadr
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pchl
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