71 lines
1.9 KiB
Z80 Assembly
71 lines
1.9 KiB
Z80 Assembly
.global scan_cards
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.global find_first_card
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.global get_all_cards
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scan_cards:
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; Read the types of all the cards in the system
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; The values in HL, BC, and A are destroyed
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ld hl, card_types+255
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ld bc, 0xFFFF ; Start at card 255
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scan_loop: ; Read the types of card 255 through to card 1
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in a, (c)
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ld (hl), a
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dec hl
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djnz scan_loop
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in a, (c) ; Read card 0's type
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ld (hl), a
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ret
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get_all_cards:
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; Gets the indexes of the cards with the specified type
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; IX is a pointer to the buffer to store the results in
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; B is the length of the buffer (0 is a 256 byte length)
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; C is the type of card to find
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; The zero flag is set if the buffer is full
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; The values in A, B, HL, and IX are destroyed
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ld hl, card_types+1
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gac_loop:
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ld a, (hl) ; Get card type
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cp c ; Check whether the type of the current card is the type we want
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jp nz, gac_next ; Skip the card if it is not
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ld (ix), l
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inc ix
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dec b
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gac_next:
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inc hl ; Go to the next card
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ld a, l ; Check if we have gone through all the cards
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or a ; (or a == cp 0)
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jp Z, gac_done ; If so, return
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ld a, b ; Check if we have filled the buffer
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or a ; (or a == cp 0)
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jp Z, gac_full ; If so, return with the zero flag set
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jp gac_loop
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gac_done:
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or 1 ; Reset zero flag to provide correct "buffer filed" indication
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gac_full:
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ret
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find_first_card:
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; Finds the first instance of a card type specified in B
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; A is zero if no such card was found, and nonzero if a card was found
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; If a card was found, the ID of the card is returned in L
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; If a card was not found, 0 is returned in L
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; The values in A and H are destroyed
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ld hl, card_types+1
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ffc_loop:
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ld a, (hl) ; Get card type
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cp b ; Check whether the type of the current card is the type we want
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jp Z, ffc_done ; If so, return the type in L
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or a ; (or a == cp 0) Check whether the card type is 0 (nonexistent card)
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jp Z, ffc_notfound ; If so, return 0 in L
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inc hl ; Go to the next card
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jp ffc_loop
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ffc_notfound:
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ld l, 0
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ffc_done:
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ret
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.bss
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.balign 256
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card_types: .ds.b 256
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