version: "1.0.1" name: fdc-expert description: Expert on NEC µPD765 Floppy Disk Controller for ES-1841. Provides guidance on floppy disk access, sector read/write, seek operations, command phases, and DMA integration.
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.