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049f2cf222
Sending the escape after its target made things complicated for upcoming stuff I want to add. Although it makes `recv.asm` slightly larger, it's really worth it.
46 lines
930 B
NASM
46 lines
930 B
NASM
.equ COM_DRV_ADDR 0x0238 ; replace with *CL's DCB addr
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.equ DEST_ADDR 0x3000 ; memory address where to put contents.
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; We process the 0x20 exception by pre-putting a mask in the (HL) we're going
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; to write to. If it wasn't a 0x20, we put a 0xff mask. If it was a 0x20, we
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; put a 0x7f mask.
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ld hl, DEST_ADDR
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loop:
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ld a, 0xff
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ld (hl), a ; default mask
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loop2:
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ld a, 0x03 ; @GET
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ld de, COM_DRV_ADDR
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rst 0x28
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jr nz, maybeerror
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or a
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ret z ; Sending a straight NULL ends the comm.
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; @PUT that char back
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ld c, a
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ld a, 0x04 ; @PUT
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rst 0x28
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jr nz, error
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ld a, c
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cp 0x20
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jr z, escapechar
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; not an escape char, just apply the mask and write
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and (hl)
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ld (hl), a
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inc hl
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jr loop
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escapechar:
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; adjust by setting (hl) to 0x7f
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res 7, (hl)
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jr loop2
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maybeerror:
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; was it an error?
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or a
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jr z, loop2 ; not an error, just loop
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; error
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error:
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ld c, a ; Error code from @GET/@PUT
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ld a, 0x1a ; @ERROR
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rst 0x28
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ret
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