Delay code: Difference between revisions
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=== 31..65566 cycles of delay === | === 31..65566 cycles of delay === | ||
;;;;;;;;;;;;;;;;;;;;;;;; | <pre>;;;;;;;;;;;;;;;;;;;;;;;; | ||
; Delays A:X clocks+overhead | ; Delays A:X clocks+overhead | ||
; Time: 256*A+X+31 clocks (including JSR) | ; Time: 256*A+X+31 clocks (including JSR) | ||
Revision as of 14:14, 14 March 2016
Delay code
Functions that cause a parametrised number of cycles of delay.
25..280 cycles of delay
;;;;;;;;;;;;;;;;;;;;;;;;
; Delays A clocks + overhead
; Preserved: X, Y
; Time: A+25 clocks (including JSR)
;;;;;;;;;;;;;;;;;;;;;;;;
: sbc #7 ; carry set by CMP
delay_a_25_clocks:
cmp #7
bcs :- ; do multiples of 7
lsr a ; bit 0
bcs :+
; A=clocks/2, either 0,1,2,3
beq @zero ; 0: 5
lsr a
beq :+ ; 1: 7
bcc :+ ; 2: 9
@zero: bne :+ ; 3: 11
: rts ; (thanks to dclxvi for the algorithm)
33..65568 cycles of delay
;;;;;;;;;;;;;;;;;;;;;;;;
; Delays A:X clocks+overhead
; Time: 256*A+X+33 clocks (including JSR)
; Clobbers A. Preserves X,Y. Has relocations.
;;;;;;;;;;;;;;;;;;;;;;;;
: ; do 256 cycles. ; 5 cycles done so far. Loop is 2+1+ 2+3+ 1 = 9 bytes.
sbc #1 ; 2 cycles - Carry was set from cmp
pha ; 3 cycles
lda #(256-25-10-2-4) ; +2
jsr delay_a_25_clocks
pla ; 4 cycles
delay_256a_x_33_clocks:
cmp #1 ; +2; 2 cycles overhead
bcs :- ; +2; 4 cycles overhead
; 0-255 cycles remain, overhead = 4
txa ; +2; 6; +27 = 33
; 15 + JSR + RTS overhead for the code below. JSR=6, RTS=6. 15+12=27
; ; Cycles Accumulator Carry flag
; ; 0 1 2 3 4 (hex) 0 1 2 3 4
sec ; 0 0 0 0 0 00 01 02 03 04 1 1 1 1 1
: sbc #5 ; 2 2 2 2 2 FB FC FD FE FF 0 0 0 0 0
Jcs :- ; 4 4 4 4 4 FB FC FD FE FF 0 0 0 0 0
lsr a ; 6 6 6 6 6 7D 7E 7E 7F 7F 1 0 1 0 1
Jcc :+ ; 8 8 8 8 8 7D 7E 7E 7F 7F 1 0 1 0 1
: sbc #$7E ;10 11 10 11 10 FF FF 00 00 01 0 0 1 1 1
Jcc :+ ;12 13 12 13 12 FF FF 00 00 01 0 0 1 1 1
Jeq :+ ; 14 15 14 00 00 01 1 1 1
Jne :+ ; 16 01 1
: rts ;15 16 17 18 19 (thanks to dclxvi for the algorithm)
30..65565 cycles of delay
;;;;;;;;;;;;;;;;;;;;;;;; ; Delays X:A clocks+overhead ; Time: 256*X+A+30 clocks (including JSR) ; Clobbers A,X. Preserves Y. Has relocations. ;;;;;;;;;;;;;;;;;;;;;;;; delay_256x_a_30_clocks: cpx #0 ; +2 Jeq delay_a_25_clocks ; +3 (25+5 = 30 cycles overhead) ; do 256 cycles. ; 4 cycles so far. Loop is 1+1+ 2+3+ 1+3 = 11 bytes. dex ; 2 cycles pha ; 3 cycles lda #(256-25-9-2-7) ; +2 jsr delay_a_25_clocks pla ; 4 jmp delay_256x_a_30_clocks ; 3.
16..271 cycles of delay
;;;;;;;;;;;;;;;;;;;;;;;; ; Delays A*256 clocks + overhead ; Preserved: X, Y ; Time: A*256+16 clocks (including JSR) ;;;;;;;;;;;;;;;;;;;;;;;; delay_256a_16_clocks: cmp #0 bne :+ rts delay_256a_11_clocks_: : pha lda #256-19-22 jsr delay_a_25_clocks pla clc adc #-1&$FF bne :- rts
31..65566 cycles of delay
;;;;;;;;;;;;;;;;;;;;;;;; ; Delays A:X clocks+overhead ; Time: 256*A+X+31 clocks (including JSR) ; Clobbers A. Preserves X,Y. Has relocations. ;;;;;;;;;;;;;;;;;;;;;;;; : ; do 256 cycles. ; 5 cycles done so far. Loop is 2+1+ 2+3+ 1 = 9 bytes. sbc #1 ; 2 cycles - Carry was set from cmp pha ; 3 cycles lda #(256-25-10-2-4) ; +2 jsr delay_a_25_clocks pla ; 4 cycles delay_256a_x_31_clocks: cmp #1 ; +2; 2 cycles overhead bcs :- ; +2; 4 cycles overhead ; 0-255 cycles remain, overhead = 4 txa ; +2; 6; +25 = 31 ;passthru <<Place the function delay_a_25_clocks immediately following here>>
