collapseos/parts/z80/blockdev_cmds.asm
Virgil Dupras 34ee91a0d7 zasm: use blkdev IDs as input and output
This will soon allow use to seek and tell on input, which is necessary
for a second pass which is necessary for forward symbol references.

This require making `blkSel` a bit more flexible. Rather than having one
global selected blkdev, each app can select its own, in its own memory
space.
2019-05-10 19:33:34 -04:00

46 lines
721 B
NASM

; *** REQUIREMENTS ***
; blockdev
; stdio
blkBselCmd:
.db "bsel", 0b001, 0, 0
ld a, (hl) ; argument supplied
cp BLOCKDEV_COUNT
jr nc, .error ; if selection >= device count, error
push de
ld de, BLOCKDEV_GETC
call blkSel
pop de
xor a
ret
.error:
ld a, BLOCKDEV_ERR_OUT_OF_BOUNDS
ret
blkSeekCmd:
.db "seek", 0b001, 0b011, 0b001
; First, the mode
ld a, (hl)
inc hl
push af ; save mode for later
; HL points to two bytes that contain out address. Seek expects HL
; to directly contain that address.
ld a, (hl)
ex af, af'
inc hl
ld a, (hl)
ld l, a
ex af, af'
ld h, a
pop af ; bring mode back
call blkSeek
call blkTell
ld a, h
call printHex
ld a, l
call printHex
call printcrlf
xor a
ret