mirror of https://github.com/hsoft/collapseos.git
44 lines
1008 B
NASM
44 lines
1008 B
NASM
; If you find youself needing to write to an EEPROM through a shell that isn't
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; built for this, compile this dependency-less code (change memory offsets as
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; needed) and run it in a USR-like fashion.
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ld bc, 0x1000 ; bytecount to write
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ld de, 0xd000 ; source data
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ld hl, 0x2000 ; dest EEPROM memory mapping
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loop:
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ld a, (de)
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ld (hl), a
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push de ; --> lvl 1
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push bc ; --> lvl 2
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ld bc, 0x2000 ; Should be plenty enough to go > 10ms
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ld e, a ; save expected data for verification
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wait:
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; as long as writing operation is running, IO/6 will toggle at each
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; read attempt and IO/7 will be the opposite of what was written. Simply
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; wait until the read operation yields the same value as what we've
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; written
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ld a, (hl)
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cp e
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jr z, waitend
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dec bc
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ld a, b
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or c
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jr nz, wait
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; mismatch
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pop bc ; <-- lvl 2
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pop de ; <-- lvl 1
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ld a, 1 ; nonzero
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or a ; unset Z
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ret
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waitend:
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pop bc ; <-- lvl 2
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pop de ; <-- lvl 1
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inc hl
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inc de
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dec bc
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ld a, b
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or c
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jr nz, loop
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ret ; Z already set
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