Editing Writing your first FV-1 program (section)

== How an FV-1 program works ==

The FV-1 runs your program '''once per audio sample''', 32768 times a second.  There is no main loop that you write; the chip loops for you.

That gives you a hard budget of '''128 instructions'''.  Anything shorter is padded with NOPs automatically.  There is no way to spend more time on one sample than another.

Almost everything flows through a single '''accumulator''' (ACC).  You read a value into it, do arithmetic on it, and write it somewhere.  Most instructions multiply by a coefficient on the way past.

The registers you will use first:

{| class="wikitable"
! Register !! Meaning
|-
| <code>ADCL</code>, <code>ADCR</code> || Audio input, left and right
|-
| <code>DACL</code>, <code>DACR</code> || Audio output, left and right
|-
| <code>POT0</code>–<code>POT2</code> || The three control knobs, 0.0 to 1.0
|-
| <code>REG0</code>–<code>REG31</code> || General-purpose storage
|}

Coefficients are fixed-point fractions in the range −1.0 to just under 1.0.  You cannot write <code>1.0</code> and expect exactly one in every field, which is why you will see <code>0.999</code> in places where you might expect 1.