mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-11-18 06:09:08 +00:00
26 lines
1.1 KiB
ArmAsm
26 lines
1.1 KiB
ArmAsm
; From http://6502org.wikidot.com/software-delay
|
|
|
|
; 25+A cycles (including JSR), 19 bytes (excluding JSR)
|
|
;
|
|
; The branches must not cross page boundaries!
|
|
;
|
|
|
|
; Cycles Accumulator Carry flag
|
|
; 0 1 2 3 4 5 6 (hex) 0 1 2 3 4 5 6
|
|
|
|
; jsr delay_a ; 6 6 6 6 6 6 6 00 01 02 03 04 05 06
|
|
|
|
dly0: sbc #7
|
|
delay_a:cmp #7 ; 2 2 2 2 2 2 2 00 01 02 03 04 05 06 0 0 0 0 0 0 0
|
|
bcs dly0 ; 2 2 2 2 2 2 2 00 01 02 03 04 05 06 0 0 0 0 0 0 0
|
|
lsr ; 2 2 2 2 2 2 2 00 00 01 01 02 02 03 0 1 0 1 0 1 0
|
|
bcs dly1 ; 2 3 2 3 2 3 2 00 00 01 01 02 02 03 0 1 0 1 0 1 0
|
|
dly1: beq dly2 ; 3 3 2 2 2 2 2 00 00 01 01 02 02 03 0 1 0 1 0 1 0
|
|
lsr ; 2 2 2 2 2 00 00 01 01 01 1 1 0 0 1
|
|
beq dly3 ; 3 3 2 2 2 00 00 01 01 01 1 1 0 0 1
|
|
bcc dly3 ; 3 3 2 01 01 01 0 0 1
|
|
dly2: bne dly3 ; 2 2 3 00 00 01 0 1 0
|
|
dly3: rts ; 6 6 6 6 6 6 6 00 00 00 00 01 01 01 0 1 1 1 0 0 1
|
|
;
|
|
; Total cycles: 25 26 27 28 29 30 31
|