add sleep

programs/sleep.s65

@@ -0,0 +1,41 @@
+.ifndef INCLUDE_SLEEP
+INCLUDE_SLEEP = 1
+;********************************************************************************
+; @macro Sleep
+; @param time_cs: Time to sleep in centiseconds (10^-2s = 10ms)
+; @details
+;   Interrupts might change the actual time to finish
+;********************************************************************************
+.macro Sleep time_cs
+    phx
+    ldx #time_cs
+    jsr sleep
+    plx
+.endmacro
+
+;********************************************************************************
+; @function sleep
+; @param x: Time to sleep in centiseconds (10^-2s = 10ms)
+; @details
+;   Interrupts might change the actual time to finish
+;   To be exact, time_cs is in units of 0.010244s
+;********************************************************************************
+.proc sleep
+VAR_1 = 0
+    stz VAR_1
+@loop:
+    .repeat 17
+    nop             ; 2 - i
+    .endrepeat
+    inc VAR_1       ; 3 - zp
+    bne @loop       ; 2/3 - r (2 if not taken, but here most of the time its 3)
+    ; reaching this takes 256 * (X * 2(nop) + 3(inc) + 3(bne)) - 1(last bne) cycles
+    ; with X = 17: T1 = (256×(17×2 + 3 +3) − 1) × (1/1MHz) = 0,010 239 s
+    dex             ; 2 - i
+    bne @loop       ; 2/3 - r 
+    ; with T1 = for running through VAR_1, one iteration takes 
+    ; T1 + (2(dex) + 3(bne))  × (1/1MHz) = 0,010 244 s
+    rts
+    ; so T = N * 0,010 244 s - (1(last bne) + 4(jsr) + 6(rts)) * (1/1MHz)
+.endproc
+.endif  ; guard