MC6821 peripheral interface adapter pinout
DIP-40. Two 8-bit parallel ports with handshake lines.
Two 6821s on HERO Jr. U214 ($D820-$D83F) scans the hex keypad on port A (pins 2-9), drives the motor and steering lines on port B, takes the wheel encoder on CB1 and sends sonar INIT on CB2 (pin 19). U215 ($D840-$D85F) carries the speech code on port A, speech power, sense enable, sound/light select and the serial ADC lines on port B, the sonar echo on CB1 (pin 18), speech strobe on CA2 (pin 39) and speech request on CA1 (pin 40). HERO 1 has no 6821 on its parts list.
Open the interactive 6821 PIA pinoutPins
| Pin | Name | Type | Signal |
|---|---|---|---|
| 1 | VSS | ground | Ground. |
| 2 | PA0 | io | Port A bit 0. |
| 3 | PA1 | io | Port A bit 1. |
| 4 | PA2 | io | Port A bit 2. |
| 5 | PA3 | io | Port A bit 3. |
| 6 | PA4 | io | Port A bit 4. |
| 7 | PA5 | io | Port A bit 5. |
| 8 | PA6 | io | Port A bit 6. |
| 9 | PA7 | io | Port A bit 7. |
| 10 | PB0 | io | Port B bit 0. |
| 11 | PB1 | io | Port B bit 1. |
| 12 | PB2 | io | Port B bit 2. |
| 13 | PB3 | io | Port B bit 3. |
| 14 | PB4 | io | Port B bit 4. |
| 15 | PB5 | io | Port B bit 5. |
| 16 | PB6 | io | Port B bit 6. |
| 17 | PB7 | io | Port B bit 7. |
| 18 | CB1 | ctrl | Interrupt input B1, edge-sensitive. |
| 19 | CB2 | ctrl | Control B2: interrupt input or handshake/control output, set by the B control register. |
| 20 | VCC | power | +5 V supply. |
| 21 | R/W | ctrl | Read/write from the CPU. |
| 22 | CS0 | ctrl | Chip select 0, active high. |
| 23 | /CS2 | ctrl | Chip select 2, active low. |
| 24 | CS1 | ctrl | Chip select 1, active high. |
| 25 | E | clock | Enable clock from the CPU. |
| 26 | D7 | data | Data bus bit 7. |
| 27 | D6 | data | Data bus bit 6. |
| 28 | D5 | data | Data bus bit 5. |
| 29 | D4 | data | Data bus bit 4. |
| 30 | D3 | data | Data bus bit 3. |
| 31 | D2 | data | Data bus bit 2. |
| 32 | D1 | data | Data bus bit 1. |
| 33 | D0 | data | Data bus bit 0. |
| 34 | /RESET | ctrl | Reset. Clears the control registers. |
| 35 | RS1 | ctrl | Register select 1. |
| 36 | RS0 | ctrl | Register select 0. |
| 37 | /IRQB | ctrl | Interrupt request B. Open drain. |
| 38 | /IRQA | ctrl | Interrupt request A. Open drain. |
| 39 | CA2 | ctrl | Control A2: interrupt input or handshake/control output. |
| 40 | CA1 | ctrl | Interrupt input A1, edge-sensitive. |
Fitted in
- HERO Jr U214, U215
- Color Computer 1 U8 ($FF00, keyboard) / U4 ($FF20, sound, cassette, RS-232)
- Color Computer 2 U7 ($FF00, keyboard) / U2 ($FF20, sound, cassette, RS-232)
- Color Computer 3 IC5 ($FF00, keyboard) / IC4 ($FF20, sound, cassette, RS-232)
- Dragon 32 IC26 ($FF00, keyboard, joystick, printer data) / IC35 ($FF20, DAC, cassette, printer handshake, VDG mode)
- Dragon 64 IC5 ($FF00) / IC8 ($FF20)