PSG Registers R0 - R2
From Intellivision Wiki
The lowest 8 bits of period for channel A, B, or C. Channel A uses R0, channel B uses R1, and channel C uses R2. See PSG Channels for more information.
0000:0000:pppp:pppp where: pppppppp indicates the lowest 8 bits of 12-bit period for channel A, B, or C