Thanks!

Here is the code:
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mainloop:
for B0 = 0 to 255
I2CWRITE SDA, SCL, $40, 0, [B0]
pause 500
next B0

pause 1000

for B0 = 255 to 0 step -1
I2CWRITE SDA, SCL, $40, 0, [B0]
pause 500
next B0

goto mainloop
End

My guess is - since the PCF chip isn't doing the READ transaction - it must be built into the IC2WRITE function.
Just curious
Thanks