78 lines
1.2 KiB
ArmAsm
78 lines
1.2 KiB
ArmAsm
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.define .mon
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! Monitor call
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! Expects on stack: monitor call number
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! parameters
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! Implemented are the following monitor calls:
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! number 1: exit
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! number 3: read
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! number 4: write
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! If called with a number of a call that is not implemented,
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! a trap is generated.
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.mon: 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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pop h ! monitor call number
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mov a,l
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cpi 1
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jz monexit ! is it an exit?
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cpi 3
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jz monread ! is it a read?
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cpi 4
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jz monwrite ! is it a write?
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jmp ebadmon ! trap
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monexit:
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rst 4
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monread:
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pop h ! file-descriptor, not used
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pop h ! hl = pointer to output buffer
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pop d ! de = number of bytes to be read
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lxi b,0 ! bc will contain the number of bytes actually read
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1: mov a,d
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ora e
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jz 2f
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call getchar
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push psw
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call putchar ! echo character
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pop psw
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mov m,a
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inx h
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inx b
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dcx d
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cpi 0x0A ! is it a newline?
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jnz 1b
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2: push b
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lxi h,0
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push h
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jmp monret
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monwrite:
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pop h ! file-descriptor, not used
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pop h ! hl = pointer to output buffer
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pop d ! de = number of bytes
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push d
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1: mov a,e
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ora d
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jz 2f
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mov a,m
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call putchar
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inx h
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dcx d
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jmp 1b
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2: push d ! no error
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jmp monret
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monret:
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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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