CEILING

; CEILING reference: a rising sawtooth 0,1,...,127 that hits a CEILING at 128 and
; snaps back to 0. Unlike RAMP it does not ride the 256 wrap; r0 is COMPARED to the
; ceiling each tick and the loop resets when it reaches it. Teaches cmp + a conditional
; jump (jl): jump back to keep climbing while below the ceiling, else reset to 0.
top:
      mov  r0, 0
loop:
      out  p0, r0       ; draw the current level
      slp  1            ; one tick per level
      inc  r0           ; next level
      cmp  r0, 128      ; reached the ceiling?
      jl   loop         ; below 128 -> keep climbing
      jmp  top          ; at the ceiling -> reset to 0

# CEILING. ACT 1, analog. A rising sawtooth that does NOT ride the automatic 256 wrap
# like RAMP: it climbs to a CEILING at 128 and snaps back to 0. The level is COMPARED
# to the ceiling each tick and reset when it reaches it, so this board teaches cmp and
# a conditional jump (the first SCOPE board with real branching). Reference is
# sc_a1_08_ceiling.asm.
# TITLE CEILING
# OBJECTIVE A rising sawtooth 0..127, capped by a compare, then a snap back to 0.
ID sc_a1_08_ceiling
WINDOW 264
DIR p0 OUT
PERIPH DAC data=p0 label=DAC_on_p0
CHAN p0 ANALOG label=CH1_p0_DAC
PAR power=1325 lines=9 chips=1