Custom Chip Registers

From Amiga Coding
Jump to: navigation, search

Custom chip registers are used for interacting with the custom chips on the Amiga. Some registers are read-only, others are write-only; care must be taken to respect. Undefined bits should always be cleared when writing, and other bits should be left in their current state to avoid upsetting other functions.

You will notice that all registers are contained within the 4KB address range $DFFxxx. Often the addresses are documented as a 12-bit address, in which case the $DFF prefix is assumed.

Unless otherwise stated, all accesses are 16-bit words.

Address Register Read/Write Chip OCS ECS AGA Function
DFF09E ADKCON W Paula Audio, disk, control write
DFF010 ADKCONR R Paula Audio, disk, control read
DFF0A0 AUD0LCH W Agnus ✓* Audio channel 0 location (high 3 bits, 5 bits if ECS)
DFF0A2 AUD0LCL W Agnus Audio channel 0 location (low 15 bits)
DFF0A4 AUD0LEN W Paula Audio channel 0 length
DFF0A6 AUD0PER W Paula ✓* Audio channel 0 period
DFF0A8 AUD0VOL W Paula Audio channel 0 volume
DFF0AA AUD0DAT W Paula Audio channel 0 data
DFF0B0 - DFF0DA Repeat of Channel 0 audio registers, DFF0Bx for channel 1, DFF0Cx for channel 2, DFF0Dx for channel 3

* Changes were made starting with this revision of chip. See Hardware Reference Manual for details.