Producing tone with Audio Codec on NIOS II?

Hey everyone,

I'm just learning how to use the Audio CODEC on NIOS II with the DE2 board. I wrote the following assembly code to generate a square wave and use it to produce an output tone:

.equ ADDR_AUDIODACFIFO, 0x10003040

.global main

main:

movia r2, ADDR_AUDIODACFIFO

# Set up the square wave's positive pulse

preloop1:

movi r3, 10000

movi r4, 22

# Send 22 outputs to the FIFO

loop1:

stwio r3, 8(r2)

stwio r3, 12(r2)

subi r4, r4, 1

beq r4, r0, preloop2

br loop1

# Set up the square wave's negative pulse

preloop2:

movi r3, -10000

movi r4, 22

# Send 22 outputs to the FIFO

loop2:

stwio r3, 8(r2)

stwio r3, 12(r2)

subi r4, r4, 1

beq r4, r0, preloop1

br loop2

It doesn't seem to be working - nothing is being written to the audio codec's FIFOs. Does anyone know what I need to do to produce a tone? Thanks.