mirror of https://github.com/cc65/cc65.git
205 lines
7.2 KiB
ArmAsm
205 lines
7.2 KiB
ArmAsm
;
|
|
; unsigned char kbhit (void);
|
|
;
|
|
; The method to detect a pressed key is based on the documentation in
|
|
; "Section 3 Programmed Key Functions" in "The Challenger Character Graphics
|
|
; Reference Manual"
|
|
; We only want to return true for characters that can be returned by cgetc(),
|
|
; but not for keys like <Shift> or <Ctrl>. Therefore a special handling is
|
|
; needed for the first row. This is implemented by a bit mask that is stored
|
|
; in tmp1 and that is set to zero after the first round.
|
|
;
|
|
|
|
.constructor initkbhit
|
|
.export _kbhit
|
|
.include "osic1p.inc"
|
|
.include "extzp.inc"
|
|
.include "zeropage.inc"
|
|
|
|
; Internal state that needs to be preserved across calls.
|
|
.segment "EXTZP" : zeropage
|
|
|
|
LASTSCAN: .res 1 ; Result of previous keyboard scan
|
|
DBNCCNT: .res 1 ; Debounce counter
|
|
KBDTMP: .res 1 ; Temporary values
|
|
CTRLSHIFT: .res 1 ; State of CTRL and SHIFT keys
|
|
|
|
; Initialize one-character buffer that is filled by kbhit()
|
|
.segment "ONCE"
|
|
initkbhit:
|
|
lda #$00
|
|
sta CHARBUF ; No character in buffer initially
|
|
|
|
sta LASTSCAN ; Initialize keyboard state
|
|
sta DBNCCNT
|
|
sta KBDTMP
|
|
sta CTRLSHIFT
|
|
|
|
rts
|
|
|
|
; Routine to get character from keyboard and return it in A.
|
|
; Based on the OSI ROM routine at $FD00 but uses different
|
|
; storage locations to avoid corrupting CC65 run-time code.
|
|
|
|
_kbhit: lda CHARBUF ; Check for previously saved character
|
|
beq LFD05
|
|
ldx #$00 ; High byte of return is always zero
|
|
rts ; A contains non-zero character code meaning true
|
|
LFD05: lda #$80 ; Bit mask for initial keyboard row
|
|
LFD06: jsr LFCBE ; Write keyboard row
|
|
jsr LFCC6 ; Read keyboard column
|
|
bne LFD13 ; Branch if a key in this column was pressed
|
|
lsr a ; Otherwise shift mask to next row
|
|
bne LFD06 ; If not done yet, check next row
|
|
beq LFD3A ; Branch if last row reached and no key pressed
|
|
LFD13: lsr a ; Have a key press. Shift LSB into carry
|
|
bcc LFD1F ; Branch if no key pressed in column 0
|
|
txa ; Key pressed in row zero. Get the column data
|
|
and #$20 ; Mask only the bit for <ESC> as it is the only key in row zero that returns key press
|
|
beq LFD3A ; Branch if <ESC> was not the key
|
|
lda #$1B ; Set character to <ESC>
|
|
bne LFD50 ; Do more processing
|
|
LFD1F: jsr LFE86 ; Shift to find bit that is set (in Y)
|
|
tya ; Get bit
|
|
sta KBDTMP ; Save it
|
|
asl a ; Multiply by 7 by shifting left three times (X8)...
|
|
asl a
|
|
asl a
|
|
sec ; ...then subtracting one
|
|
sbc KBDTMP
|
|
sta KBDTMP ; Save value*7 for later lookup in table
|
|
txa ; Get the keyboard column
|
|
lsr a ; Shift out bit zero (only key there is <SHIFT LOCK>)
|
|
asl a ; And shift back
|
|
jsr LFE86 ; Shift to find bit that is set (in Y)
|
|
beq LFD47 ; Branch if no keys pressed
|
|
lda #$00
|
|
LFD3A: sta CTRLSHIFT ; Save state of <CTRL> and shift keys
|
|
LFD3D: sta LASTSCAN
|
|
lda #$02 ; Count used for key debouncing
|
|
sta DBNCCNT
|
|
ldx #$00 ; High byte of return is always zero
|
|
lda #$00 ; Return false
|
|
rts
|
|
LFD47: clc
|
|
tya ; Get bit number of pressed key
|
|
adc KBDTMP ; Add previously calculated offset for keyboard row*7
|
|
tay
|
|
lda LFF3B,y ; Read ASCII code for key from table
|
|
LFD50: cmp LASTSCAN ; Debounce - same as last key scan?
|
|
bne LFD3D ; If not, try again
|
|
dec DBNCCNT ; Decrement debounce counter
|
|
beq LFD5F ; Branch if done debouncing
|
|
jsr LFCDF ; Wait for short delay to debounce keyboard
|
|
beq _kbhit ; Go back and scan keyboard.
|
|
LFD5F: ldx #$64 ; Was <CONTROL> key down?
|
|
cmp CTRLSHIFT
|
|
bne LFD68 ; Branch if not
|
|
ldx #$0F
|
|
LFD68: stx DBNCCNT
|
|
sta CTRLSHIFT
|
|
cmp #$21
|
|
bmi LFDD0 ; Done, return key
|
|
cmp #$5F
|
|
beq LFDD0 ; Done, return key
|
|
lda #$01
|
|
jsr LFCBE ; Write keyboard row
|
|
jsr LFCCF ; Read keyboard column
|
|
sta KBDTMP
|
|
tax
|
|
and #$06
|
|
bne LFDA2
|
|
bit LASTSCAN
|
|
bvc LFDBB
|
|
txa
|
|
eor #$01
|
|
and #$01
|
|
beq LFDBB
|
|
lda #$20
|
|
bit KBDTMP
|
|
bvc LFDC3
|
|
lda #$C0
|
|
bne LFDC3
|
|
LFDA2: bit LASTSCAN
|
|
bvc LFDAA
|
|
txa
|
|
beq LFDBB
|
|
LFDAA: ldy LASTSCAN
|
|
cpy #$31
|
|
bcc LFDB9
|
|
cpy #$3C
|
|
bcs LFDB9
|
|
lda #$F0
|
|
bne LFDBB
|
|
LFDB9: lda #$10
|
|
LFDBB: bit KBDTMP
|
|
bvc LFDC3
|
|
clc
|
|
adc #$C0
|
|
LFDC3: clc
|
|
adc LASTSCAN
|
|
and #$7F
|
|
bit KBDTMP
|
|
bpl LFDD0
|
|
ora #$80
|
|
LFDD0: sta KBDTMP ; Save pressed key and return in A
|
|
sta CHARBUF
|
|
rts
|
|
|
|
; Write keyboard row with value in A.
|
|
; Invert the bits before writing.
|
|
; Returns original value of A.
|
|
|
|
LFCBE: eor #$FF
|
|
sta KBD
|
|
eor #$FF
|
|
rts
|
|
|
|
; Read keyboard column and return in X.
|
|
; Sets Z flag if no keys were pressed.
|
|
; Saves current value of A.
|
|
|
|
LFCC6: pha ; Save A
|
|
jsr LFCCF ; Read keyboard column
|
|
tax ; Save in X
|
|
pla ; Restore A
|
|
dex ; Decrement and then increment to
|
|
inx ; preserve value of X but set flags
|
|
rts
|
|
|
|
; Read keyboard column.
|
|
; Invert the bits (pressed key(s) will show up as ones).
|
|
|
|
LFCCF: lda KBD ; Read keyboard hardware
|
|
eor #$FF ; Invert the bits
|
|
rts
|
|
|
|
; Short fixed delay routine.
|
|
|
|
LFCDF: ldy #$10
|
|
LFCE1: ldx #$40
|
|
LFCE3: dex
|
|
bne LFCE3
|
|
dey
|
|
bne LFCE1
|
|
rts
|
|
|
|
; Shift A left until we find a 1 in the most significant bit.
|
|
; Return the bit number in Y.
|
|
|
|
LFE86: ldy #$08
|
|
LFE88: dey
|
|
asl a
|
|
bcc LFE88
|
|
rts
|
|
|
|
; Lookup table of keyboard keys for each scan row.
|
|
LFF3B: .byte $BD
|
|
.byte 'P', ';', '/', ' ', 'Z', 'A', 'Q'
|
|
.byte ',', 'M', 'N', 'B', 'V', 'C', 'X'
|
|
.byte 'K', 'J', 'H', 'G', 'F', 'D', 'S'
|
|
.byte 'I', 'U', 'Y', 'T', 'R', 'E', 'W'
|
|
.byte $00, $00, $0D, $0A, 'O', 'L', '.'
|
|
.byte $00, '_', '-', ':', '0', '9', '8'
|
|
.byte '7', '6', '5', '4', '3', '2', '1'
|