WD1770 / WD1772 floppy disk controller pinout
DIP-28. Single and double density floppy disk controller with built-in data separator and write precompensation.
A 179X-compatible controller with its own data separator and write precompensation, needing an 8 MHz clock on pin 18. The 1772 is the same chip with faster step rates. On the Master DRQ (pin 27) is inverted onto the CPU NMI by the I/O controller; INTRQ stuck high masks DRQ. Drive select and side come from a 74LS174 latch (IC4). Master probing (SM 7.8): /CS (pin 1) goes validly low when the filing system accesses the chip; the 8 MHz on pin 18 comes from IC19 pin 4 and VIDPROC pin 7; DRQ (pin 27) is low, going high once every 32 us while reading.
Open the interactive 1770 pinoutPins
| Pin | Name | Type | Signal |
|---|---|---|---|
| 1 | /CS | ctrl | Chip select. |
| 2 | R/W | ctrl | High = read, low = write. |
| 3 | A0 | addr | Register select bit 0. |
| 4 | A1 | addr | Register select bit 1 (status/command, track, sector, data). |
| 5 | DAL0 | data | Data bus bit 0. |
| 6 | DAL1 | data | Data bus bit 1. |
| 7 | DAL2 | data | Data bus bit 2. |
| 8 | DAL3 | data | Data bus bit 3. |
| 9 | DAL4 | data | Data bus bit 4. |
| 10 | DAL5 | data | Data bus bit 5. |
| 11 | DAL6 | data | Data bus bit 6. |
| 12 | DAL7 | data | Data bus bit 7. |
| 13 | /MR | ctrl | Master reset (internal pull-up). |
| 14 | GND | ground | Ground. |
| 15 | VCC | power | +5 V +/-5%. |
| 16 | STEP | ctrl | Step pulse per head step. |
| 17 | DIRC | ctrl | Direction: high = stepping in. |
| 18 | CLK | clock | 8 MHz, 50% duty clock. |
| 19 | /RD | data | Raw read data from the drive. |
| 20 | MO | ctrl | Motor on. |
| 21 | WG | ctrl | Write gate. |
| 22 | WD | data | Write data (FM or MFM pulses). |
| 23 | /TR00 | ctrl | Track 00 (internal pull-up). |
| 24 | /IP | ctrl | Index pulse (internal pull-up). |
| 25 | /WPRT | ctrl | Write protect (internal pull-up). |
| 26 | /DDEN | ctrl | Low = double density (MFM). |
| 27 | DRQ | ctrl | Data request. |
| 28 | INTRQ | ctrl | Interrupt request: set HIGH when a command completes; it stays HIGH until the Status Register is read or a new command is written. |
Fitted in
- BBC Master 128 IC3
- BBC Micro Model B 1770 upgrade daughter board (replaces the 8271)
- Commodore 1571 disk drive U11 (WD1770 or WD1772, $2000-$2003)
- Commodore 1581 disk drive U4 (WD1770, or WD1772 with J1 removed; $6000-$6003)