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8bitworkshop/presets/vcs/xtimer.inc
2018-08-27 16:50:53 -04:00

42 lines
1.7 KiB
SQL

; Set up macro for timer table
MAC TIMER_TABLE_SETUP
lda #255
sta WSYNC
sta TIM64T
ENDM
; Timer -> Scanline table
Timer2Scanline
.byte 215, 0,214,213,212,211,210, 0,209,208,207,206,205,204, 0,203
.byte 202,201,200,199, 0,198,197,196,195,194, 0,193,192,191,190,189
.byte 188, 0,187,186,185,184,183, 0,182,181,180,179,178, 0,177,176
.byte 175,174,173,172, 0,171,170,169,168,167, 0,166,165,164,163,162
.byte 0,161,160,159,158,157,156, 0,155,154,153,152,151, 0,150,149
.byte 148,147,146, 0,145,144,143,142,141,140, 0,139,138,137,136,135
.byte 0,134,133,132,131,130, 0,129,128,127,126,125,124, 0,123,122
.byte 121,120,119, 0,118,117,116,115,114, 0,113,112,111,110,109,108
.byte 0,107,106,105,104,103, 0,102,101,100, 99, 98, 0, 97, 96, 95
.byte 94, 93, 92, 0, 91, 90, 89, 88, 87, 0, 86, 85, 84, 83, 82, 0
.byte 81, 80, 79, 78, 77, 76, 0, 75, 74, 73, 72, 71, 0, 70, 69, 68
.byte 67, 66, 0, 65, 64, 63, 62, 61, 60, 0, 59, 58, 57, 56, 55, 0
.byte 54, 53, 52, 51, 50, 0, 49, 48, 47, 46, 45, 44, 0, 43, 42, 41
.byte 40, 39, 0, 38, 37, 36, 35, 34, 0, 33, 32, 31, 30, 29, 28, 0
.byte 27, 26, 25, 24, 23, 0, 22, 21, 20, 19, 18, 0, 17, 16, 15, 14
.byte 13, 12, 0, 11, 10, 9, 8, 7, 0, 6, 5, 4, 3, 2, 0, 1
; Pass: A = desired scanline
; Returns: Y = timer value - 1
align $10
WaitForScanline subroutine
ldy INTIM ; Fetch timer value
.Wait
cpy INTIM
beq .Wait ; Wait for it to change
sta WSYNC ; Sync with scan line
cmp Timer2Scanline,y ; lookup scanline
bcs WaitForScanline ; repeat until >=
rts