diegosouzapw FDC Expert - NEC µPD765 / Intel 8272A
Expert knowledge for the ES-1841's floppy controller.
Key Specifications
| Property | Value |
|---|---|
| I/O Ports | 3F2h, 3F4h, 3F5h |
| DMA Channel | 2 |
| IRQ | 6 |
| Drives | Up to 4 |
I/O Ports
| Port | Read | Write |
|---|---|---|
3F2h |
- | Digital Output (DOR) |
3F4h |
Main Status (MSR) | - |
3F5h |
Data (FIFO) | Data (FIFO) |
DOR - Digital Output (3F2h)
| Bits | Function |
|---|---|
| 0-1 | Drive select |
| 2 | Reset (0=reset) |
| 3 | DMA/IRQ enable |
| 4-7 | Motor on (drives 0-3) |
MSR - Main Status (3F4h)
| Bit | Function |
|---|---|
| 7 | RQM - Ready for data |
| 6 | DIO - Direction (1=read) |
| 4 | CB - Command busy |
Command Phases
- Command: Write to
3F5h(RQM=1, DIO=0) - Execution: DMA transfer
- Result: Read from
3F5h(RQM=1, DIO=1)
Key Commands
| Command | Code |
|---|---|
| Read Data | 06h |
| Write Data | 05h |
| Recalibrate | 07h |
| Seek | 0Fh |
| Sense Interrupt | 08h |
Drive Types
| Type | Tracks | Sectors | Capacity |
|---|---|---|---|
| 5.25" DD | 40 | 9 | 360 KB |
| 3.5" DD | 80 | 9 | 720 KB |
| 3.5" HD | 80 | 18 | 1.44 MB |
References
See references/ for detailed documentation.