Programming:Unlocking ASIC

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;; This example shows how to unlock the ASIC
;; This example is designed for CPC+ only and will
;; not work on CPC or KC Compact.
;; This example will compile with the MAXAM assembler
;; or the built-in assembler of WinAPE32.

org &8000

;; Unlock CPC+ additional features

ld b,&bc
ld hl,sequence
ld e,17
ld a,(hl)
out (c),a
inc hl
dec e
jr nz,seq

;; this is the sequence to unlock the ASIC extra features
defb &ff,&00,&ff,&77,&b3,&51,&a8,&d4,&62,&39,&9c,&46,&2b,&15,&8a,&cd,&ee

Note: As one may see, the nybbles in the sequence are based on two 4bit shift registers. For one reason or another, Amstrad has patented the verification mechanism (GB2243701A). The patent seems to focus on verifying (rather than on sending) the sequence, so its legal use is a bit unclear.