Intel 8271 floppy disk controller pinout
DIP-40. Single-density (FM) floppy disk controller with internal CRC, seek and head positioning.
A high-level single-density controller at &FE80-&FE84 with internal CRC and head positioning; the BBC uses its non-DMA mode and services each byte on NMI. Data separation is external (IC81, IC82, IC87). Disk upgrades also need the DFS ROM, MOS 1.2 and a supply with the auxiliary socket. Double density needs a 1770 board instead. On the Model B: SELECT 0 (pin 2) drives disk connector pin 10 through a 7438, INT (pin 11) goes to the CPU NMI and /CS (pin 24) decodes &FE80-&FE9F.
Open the interactive 8271 pinoutPins
| Pin | Name | Type | Signal |
|---|---|---|---|
| 1 | FAULT RESET/OPO | io | Optional fault reset or general output. |
| 2 | SELECT 0 | ctrl | Drive select 0. |
| 3 | CLK | clock | Square-wave clock input. |
| 4 | RESET | ctrl | High forces the 8271 idle and drive outputs low. Hold for 10 or more clocks. |
| 5 | READY 1 | ctrl | Drive 1 ready. |
| 6 | SELECT 1 | ctrl | Drive select 1. |
| 7 | /DACK | ctrl | DMA acknowledge; used as the data register select in non-DMA mode. |
| 8 | DRQ | ctrl | Data request (one byte every 32 us at single density). |
| 9 | /RD | ctrl | Read strobe. |
| 10 | /WR | ctrl | Write strobe. |
| 11 | INT | ctrl | Interrupt: high until the result register is read. |
| 12 | DB0 | data | Data bus bit 0. |
| 13 | DB1 | data | Data bus bit 1. |
| 14 | DB2 | data | Data bus bit 2. |
| 15 | DB3 | data | Data bus bit 3. |
| 16 | DB4 | data | Data bus bit 4. |
| 17 | DB5 | data | Data bus bit 5. |
| 18 | DB6 | data | Data bus bit 6. |
| 19 | DB7 | data | Data bus bit 7. |
| 20 | GND | ground | Ground. |
| 21 | A0 | addr | Register address bit 0. |
| 22 | A1 | addr | Register address bit 1. |
| 23 | INSYNC | ctrl | High once byte sync with an address mark is found. |
| 24 | /CS | ctrl | Chip select. |
| 25 | PLO/SS | ctrl | Data separator type: phase-locked or single-shot. |
| 26 | DATA WINDOW | ctrl | Data window from the external separator. |
| 27 | UNSEP DATA | data | Unseparated clock and data from the drive. |
| 28 | FAULT | ctrl | Drive fault (file unsafe). |
| 29 | WR DATA | data | Composite write data. |
| 30 | COUNT/OPI | io | Seek count input or optional input. |
| 31 | TRK0 | ctrl | Head over track 0. |
| 32 | READY 0 | ctrl | Drive 0 ready. |
| 33 | WR PROTECT | ctrl | Disk write protected. |
| 34 | INDEX | ctrl | Index pulse. |
| 35 | WR ENABLE | ctrl | Write enable to the drive. |
| 36 | SEEK/STEP | ctrl | Step pulses. |
| 37 | DIRECTION | ctrl | High = step in toward the spindle. |
| 38 | LOAD HEAD | ctrl | Load head. |
| 39 | LOW CURRENT | ctrl | High at track 43 and up. |
| 40 | VCC | power | +5 V. |
Fitted in
- BBC Micro Model B IC78 (disk upgrade)