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1.8 KiB
1.8 KiB
The Description-Based Direct Memory Access (DBDMA) relies on memory-based descriptions, minimizing CPU interrupts.
| Channel | Number |
|---|---|
| SCSI0 | 0x0 |
| FLOPPY | 0x1 |
| ETHERNET TRANSMIT | 0x2 |
| ETHERNET RECIEVE | 0x3 |
| SCC TRANSMIT A | 0x4 |
| SCC RECIEVE A | 0x5 |
| SCC TRANSMIT B | 0x6 |
| SCC RECIEVE B | 0x7 |
| AUDIO OUT | 0x8 |
| AUDIO IN | 0x9 |
| SCSI1 | 0xA |
What's notable about the registers is that they are in little-endian format.
| Register | Offset |
|---|---|
| ChannelControl | 0x00 |
| ChannelStatus | 0x04 |
| CommandPtrHi | 0x08 |
| CommandPtrLo | 0x0C |
| InterruptSelect | 0x10 |
| BranchSelect | 0x14 |
| WaitSelect | 0x18 |
| TransferMode | 0x1C |
| Data2PtrHi | 0x20 |
| Data2PtrLo | 0x24 |
| BranchPtrHi | 0x2C |
| BranchPtrLo | 0x30 |
| Command | Value |
|---|---|
| OUTPUT_MORE | 0x0 |
| OUTPUT_LAST | 0x1 |
| INPUT_MORE | 0x2 |
| INPUT_LAST | 0x3 |
| STORE_QUAD | 0x4 |
| LOAD_QUAD | 0x5 |
| NOP | 0x6 |
| STOP | 0x7 |
| Key Name | Value |
|---|---|
| KEY_STREAM0 | 0x0 |
| KEY_STREAM1 | 0x1 |
| KEY_STREAM2 | 0x2 |
| KEY_STREAM3 | 0x3 |
| KEY_REGS | 0x5 |
| KEY_SYSTEM | 0x6 |
| KEY_DEVICE | 0x7 |