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; This code must be position-independent.
org 0
entry: ; On entry HL points here
inc h ; Buffer at +256 bytes
push hl ; Buffer address
xor a
ld l,a
ld h,a
; DE -> ROM address
; Wait for NMI before copying the first chunk
di
halt
; Test for RAM
inc a ; A = 1
out (7),a
ld c,(hl)
add c
ld (hl),a
ld a,(hl)
sub c
jr z,error ; A = 0, HL = 0 on error
copy:
xor a
out (7),a
; Copy to buffer
pop de ; Buffer address
push de ; Buffer address
push hl ; ROM address
ld bc,256
ldir
inc a ; A = 1
out (7),a
; Copy from buffer
pop de ; ROM address
pop hl ; Buffer address
push hl ; Buffer address
inc b ; BC <- 256
ldir
ex de,hl ; ROM address -> HL
bit 7,h
jr z,copy
; A = 1, HL != 0
error:
out (7),a
ei
ret
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