Pinout diagram
Used in Retro Machine Hubs
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Summary specifications
Full pin reference
| Pin | Name | Group | Direction | Levels | Description |
|---|---|---|---|---|---|
| 1 | VSS | Ground | Power | 0 V | System ground (0 V). |
| 2 | D3 | Data Bus | Bidirectional | TTL | Data bus bit 3. |
| 3 | D4 | Data Bus | Bidirectional | TTL | Data bus bit 4. |
| 4 | D5 | Data Bus | Bidirectional | TTL | Data bus bit 5. |
| 5 | D6 | Data Bus | Bidirectional | TTL | Data bus bit 6. |
| 6 | D7 | Data Bus | Bidirectional | TTL | Data bus bit 7. |
| 7 | PHI2 | Clock / Timing | Input | TTL 1.79 MHz | System Phase 2 clock input (1.79 MHz NTSC / 1.77 MHz PAL). |
| 8 | P6 (POT6) | Analog | Input | RC ramp | Paddle 6 potentiometer input. |
| 9 | P7 (POT7) | Analog | Input | RC ramp | Paddle 7 potentiometer input. |
| 10 | P4 (POT4) | Analog | Input | RC ramp | Paddle 4 potentiometer input. |
| 11 | P5 (POT5) | Analog | Input | RC ramp | Paddle 5 potentiometer input. |
| 12 | P2 (POT2) | Analog | Input | RC ramp | Paddle 2 (Joystick Port 2 Left Paddle) input. |
| 13 | P3 (POT3) | Analog | Input | RC ramp | Paddle 3 (Joystick Port 2 Right Paddle) input. |
| 14 | P0 (POT0) | Analog | Input | RC ramp | Paddle 0 (Joystick Port 1 Left Paddle) input. |
| 15 | P1 (POT1) | Analog | Input | RC ramp | Paddle 1 (Joystick Port 1 Right Paddle) input. |
| 16 | /KR2 | I/O | Input | TTL, active low | Keyboard Response 2 (reads SHIFT, CONTROL, and BREAK keys). |
| 17 | VCC | Power | Power | +5 V | +5 V main supply. |
| 18 | /K5 | I/O | Output | TTL | Keyboard scan counter bit 5 (MSB — drives CD4051 column multiplexer). |
| 19 | /K4 | I/O | Output | TTL | Keyboard scan counter bit 4. |
| 20 | /K3 | I/O | Output | TTL | Keyboard scan counter bit 3. |
| 21 | /K2 | I/O | Output | TTL | Keyboard scan counter bit 2 (drives CD4051 row multiplexer). |
| 22 | /K1 | I/O | Output | TTL | Keyboard scan counter bit 1. |
| 23 | /K0 | I/O | Output | TTL | Keyboard scan counter bit 0 (LSB). |
| 24 | SID | I/O | Input | TTL | Serial Input Data (from 13-pin SIO bus Pin 3 Data In!). |
| 25 | /KR1 | I/O | Input | TTL, active low | Keyboard Response 1 (main 64-key matrix return from CD4051 multiplexers). |
| 26 | BCLK | Clock / Timing | Bidirectional | TTL clock | Bidirectional Serial Clock (SIO Pin 1 Clock In/Out). |
| 27 | OCLK | Clock / Timing | Output | TTL clock | Serial Output Clock (SIO Pin 2 Clock Out). |
| 28 | SOD | I/O | Output | TTL | Serial Output Data (to 13-pin SIO bus Pin 5 Data Out!). |
| 29 | /IRQ | Control | Open-drain / open-collector | Open-drain, active low | Interrupt Request output to 6502C Pin 4 (Keyboard, SIO, and Timer interrupts). |
| 30 | CS0 | Control | Input | TTL, active low | Chip Select 0 (active low, mapped at $D200-$D2FF). |
| 31 | CS1 | Control | Input | TTL, active high | Chip Select 1 (active high; used on dual-POKEY stereo upgrades using A4!). |
| 32 | R/W | Control | Input | TTL | Read/Write input. |
| 33 | A3 | Address Bus | Input | TTL | Register address bit 3. |
| 34 | A2 | Address Bus | Input | TTL | Register address bit 2. |
| 35 | A1 | Address Bus | Input | TTL | Register address bit 1. |
| 36 | A0 | Address Bus | Input | TTL | Register address bit 0. |
| 37 | AUDIO | Analog | Output | Analog audio | 4-channel mixed audio output. |
| 38 | D0 | Data Bus | Bidirectional | TTL | Data bus bit 0. |
| 39 | D1 | Data Bus | Bidirectional | TTL | Data bus bit 1. |
| 40 | D2 | Data Bus | Bidirectional | TTL | Data bus bit 2. |
Common uses and repair diagnostics
Designed by Doug Neubauer (who also programmed Star Raiders!), the 40-pin Atari POKEY (Potentiometer and Keyboard Integrated Circuit, part number CO12294) is one of the most versatile I/O and sound chips of the 8-bit era. In a single 40-pin DIP it packs: (1) a 4-channel square-wave + polynomial distortion audio synthesizer (combinable into two 16-bit precision channels!), (2) a 6-bit counter (K0-K5) that scans the 64-key keyboard matrix via two external CD4051 multiplexers, (3) eight 8-bit capacitor-discharge ADCs (P0-P7) for reading up to 8 Atari paddles, (4) a 17-bit polynomial random-number generator ($D20A RANDOM), and (5) the high-speed bidirectional UART driving the 13-pin Atari SIO peripheral bus!
Used in every Atari 8-bit computer (400, 800, 1200XL, 600XL, 800XL, 65XE, 130XE, XEGS), the Atari 5200, Atari 7800 cartridges (Ballblazer, Commando), and dozens of Atari arcade cabinets (Centipede, Millipede, Missile Command, Tempest, Star Wars, Major Havoc, Gauntlet, Return of the Jedi — many using Dual or Quad POKEYs!).
- Wait before blaming POKEY for a dead keyboard! On the 800XL and 130XE, two cheap 16-pin CD4051 CMOS analog multiplexers (U18 and U19) sit between the keyboard and POKEY Pins 18-23 (/K0-/K5) and Pin 25 (/KR1). Static electricity blows the CD4051s far more often than POKEY!
- If a 1050 disk drive or FujiNet/SDrive-MAX is ignored on the SIO port, check POKEY Pin 24 (SID) and Pin 28 (SOD) — and also check 6520 PIA Pin 19 (CB2 /COMMAND)!