terom@46: ;; vim: set ft=avr:
terom@17: ;;
terom@17: ;; Busy-loop delays
terom@17: ;;
terom@17: 
terom@17: ;; Delay for approx. one second
terom@17: Delay_1s:
terom@17:         ; ~16M cycles
terom@17:         ldi         r20, 82
terom@17:         rjmp        delay_init
terom@17: 
terom@17: ;; Delay for a variable amount of time, adjusted by r20
terom@17: ; Input: r20 controls number of delay loops
terom@17: VarDelay:
terom@17:         tst         r20
terom@17:         breq        delay_out
terom@17: 
terom@17: delay_init:
terom@17:         ldi         r21, 255
terom@17: 
terom@17: delay_loop:
terom@17:         ; 254 * (1 + 2) + 1 * (1 + 1) = 764 cycles / loop
terom@17:         dec         r22             
terom@17:         brne        delay_loop
terom@17: 
terom@17:         ; 254 * 764 + 764 = 194820 cycles / loop
terom@17:         dec         r21             ;  1 * r20 * r21
terom@17:         brne        delay_loop      ;  2 * r20 * r21
terom@17:         
terom@17:         ; r20 * 194820 + r20 * 3 = 194823 cycles / loop (r20)
terom@17:         dec         r20             ;  1 * r20 
terom@17:         brne        delay_loop      ;  2 * r20
terom@17: 
terom@17: delay_out:
terom@17:         ret
terom@17: 
terom@17: