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collapseos/apps/at28w/main.asm
2019-12-29 21:02:04 -05:00

79 lines
1.4 KiB
NASM

; *** Consts ***
; Memory address where the AT28 is configured to start
.equ AT28W_MEMSTART 0x2000
; Value mismatch during validation
.equ AT28W_ERR_MISMATCH 0x10
; *** Variables ***
.equ AT28W_MAXBYTES AT28W_RAMSTART
.equ AT28W_RAMEND @+2
; *** Code ***
at28wMain:
ld de, AT28W_MAXBYTES
ld a, (hl)
or a
jr z, at28wInner ; no arg
call parseHexadecimal ; --> DE
jr z, at28wInner
; bad args
ld a, SHELL_ERR_BAD_ARGS
ret
at28wInner:
; Reminder: words in parseArgs aren't little endian. High byte is first.
ld a, (AT28W_MAXBYTES)
ld b, a
ld a, (AT28W_MAXBYTES+1)
ld c, a
ld hl, AT28W_MEMSTART
call at28wBCZero
jr nz, .loop
; BC is zero, default to 0x2000 (8k, the size of the AT28)
ld bc, 0x2000
.loop:
call blkGetB
jr nz, .loopend
ld (hl), a
ld e, a ; save expected data for verification
; initiate polling
ld a, (hl)
ld d, a
.wait:
; as long as writing operation is running, IO/6 will toggle at each
; read attempt. We know that write is finished when we read the same
; value twice.
ld a, (hl)
cp d
jr z, .waitend
ld d, a
jr .wait
.waitend:
; same value was read twice. A contains our final value for this memory
; address. Let's compare with what we're written.
cp e
jr nz, .mismatch
inc hl
dec bc
call at28wBCZero
jr nz, .loop
.loopend:
; We're finished. Success!
xor a
ret
.mismatch:
ld a, AT28W_ERR_MISMATCH
ret
at28wBCZero:
xor a
cp b
ret nz
cp c
ret