|
- ;----------------------
- ; Utility Subroutines
- ;----------------------
-
- SECTION "Util Subs", ROM0
-
- ; MemCpy assumes:
- ; hl contains destination address
- ; de contains source address
- ; bc contains number of bytes to copy
-
- MemCpy:
- .copy
- ld a, [de]
- ld [hli], a
- inc de
- dec bc
- ld a, b
- or c
- jr nz, .copy
- ret
-
- ; Read_Pad will set the variable _PAD
- ; such that bits are as follows:
- ; 7 - 4: down up left right
- ; 3 - 0: start select b a
-
- Read_Pad:
- ld a,P1F_BUTTONS
- call .onenibble
- ld b,a ; B7-4 = 1; B3-0 = unpressed buttons
-
- ld a,P1F_DPAD
- call .onenibble
- swap a ; A3-0 = unpressed directions; A7-4 = 1
- xor b ; A = pressed buttons + directions
- ld b,a ; B = pressed buttons + directions
- ; check illegal buttons
- and %11000000 ; Up and Down buttons
- cp %11000000
- jr nz, .legalUpDown
- ld a, b
- and %00111111
- ld b, a
- .legalUpDown
- and %00110000 ; Left and Right buttons
- cp %00110000
- jr nz, .legalLeftRight
- ld a, b
- and %11001111
- .legalLeftRight
- ld a,P1F_NONE
- ld [rP1],a
-
- ldh a,[hCurKeys]
- xor b ; A = keys that changed state
- and b ; A = keys that changed to pressed
- ldh [hNewKeys],a
- ld a,b
- ldh [hCurKeys],a
- ret
-
- .onenibble:
- ldh [rP1],a
- ldh a,[rP1]
- ldh a,[rP1]
- ldh a,[rP1]
- or $F0
- ret
|
