Editing Writing your first FV-1 program (section)

== The finished tremolo ==

<pre>
; Simple tremolo
; POT0 = rate, POT1 = depth

EQU	mod	REG0

; Start the sine LFO once, on the first pass only
SKP	RUN, loop
WLDS	SIN0, 40, 32767

loop:
; POT0 sets the LFO rate
RDAX	POT0, 0.5
SOF	1.0, 0.02
WRAX	SIN0_RATE, 0.0

; Read the LFO and fold it into a 0..1 gain
CHO	RDAL, SIN0
SOF	0.5, 0.5
MULX	POT1
SOF	-1.0, 0.999
WRAX	mod, 0.0

; Apply the gain to both channels
RDAX	ADCL, 1.0
MULX	mod
WRAX	DACL, 0.0

RDAX	ADCR, 1.0
MULX	mod
WRAX	DACR, 0.0
</pre>

Sixteen instructions, out of the 128 available.

Two new things appear here.  <code>EQU mod REG0</code> gives <code>REG0</code> a readable name — the assembler substitutes it, and it costs nothing at runtime.  Writing to <code>SIN0_RATE</code> changes the LFO rate while the program runs, which is what turns POT0 into a rate knob; the <code>SOF 1.0, 0.02</code> keeps the rate from reaching zero at the bottom of the sweep.

Load it into the simulator, press Play, and move POT0 and POT1.