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All offsets from the base address of the chip
| Starting offset | Function |
|---|---|
| 0x000 | FIFO A |
| 0x400 | FIFO B |
| 0x800 | Version (read-only) EASC returns 0xB0. |
| 0x801 | Mode: 0 = disable (repeat last sample output infinitely), 1 = run |
| 0x802 | Overflow flag: bit 7 set if engine overrun |
| 0x803 | FIFO clear strobe (bit 7) |
| 0x804 | FIFO interrupt status: bit 0 = A half full, bit 1 = A full/empty, bit 2 = B half full, bit 3 = B full/empty |
| 0x806 | Volume control (top 3 bits only) |
| 0x807 | Clock rate select on ASC: hardwired to return 0x03 here |
| 0x80A | Channel A play/record: bit 0 = 0 for play, 1 for record, bit 1 = 0 for 11 kHz record, 1 for 22 kHz record |
| 0x80F | Test logic control (bit 7) |
| 0xF00 | A write pointer high |
| 0xF01 | A write pointer low |
| 0xF02 | A read pointer high |
| 0xF03 | A read pointer low |
| 0xF04 | A sample rate time increment high |
| 0xF05 | A sample rate time increment low |
| 0xF06 | A left volume |
| 0xF07 | A right volume |
| 0xF08 | A FIFO control (bit 7 = 1 to enable CD-XA decompression) |
| 0xF09 | A interrupt control (bit 0 = 1 to enable buffer half-full IRQ) |
| 0xF10-0xF17 | A CD-XA decompression filter constants |
| 0xF20 | B write pointer high |
| 0xF21 | B write pointer low |
| 0xF22 | B read pointer high |
| 0xF23 | B read pointer low |
| 0xF24 | B sample rate time increment high |
| 0xF25 | B sample rate time increment low |
| 0xF26 | B left volume |
| 0xF27 | B right volume |
| 0xF28 | B FIFO control (bit 7 = 1 to enable CD-XA decompression) |
| 0xF29 | B interrupt control (bit 0 = 1 to enable buffer half-full IRQ) |
| 0xF30-0xF37 | B CD-XA decompression filter constants |
Notes: - The filter constants for CD-XA mode are programmable. By default they are the values from the Yellow Book spec: 0x00, 0x00, 0x00, 0x3C, 0xCC, 0x73, 0xC9, 0x62. - The two FIFO spaces do not differentiate between addresses inside of them: a read or write anywhere in 000-0x3FF will read/write the next byte for FIFO A. On the original ASC this was true of normal sample playback mode but not wavetable mode. EASC does not support wavetable mode.