Dragon 32
A CoCo chipset on a sturdy PAL board, with a parallel printer port and a transformer brick.
Open the Dragon 32 in Retro Bench- Also
- D32; rebadged by Finlux, Farm Fax and ATV
- Year
- 1982
- CPU
- 6809E @ 0.89 MHz
- RAM
- 32 KB (16 × 4116, or 8 × OKI 3732 "half-good" 64K on some boards)
- ROM
- 16 KB Microsoft Extended Color BASIC 1.0 (2 × 8 KB MCM68A364)
- Video
- MC6847 VDG with PAL line insertion and an LM1889 color encoder: 32 × 16 text, PMODE 0–4 up to 256 × 192
- Sound
- 6-bit DAC and single-bit sound from the $FF20 PIA, through the 4529 mux
- OS
- Microsoft Extended Color BASIC (Dragon tokens)
Chips
| Chip | Where | Role |
|---|---|---|
| MC6883 synchronous address multiplexer | IC15 (74LS783) | Makes all clocks from the 14.31818 MHz crystal, the DRAM strobes and address multiplex, and the device selects. Used in the CoCo 1 and 2 and the Dragon 32 and 64. |
| MC6809E microprocessor | IC19 | Main CPU, 8-bit with 16-bit registers. Same CPU in every CoCo and in the Dragon 32 and 64. |
| MC6847 video display generator | IC12 | Text, semigraphics and color video from screen RAM. Used in the CoCo 1 and 2, the MC-10 and the Dragon 32 and 64. |
| MC6821 peripheral interface adapter | IC26 ($FF00, keyboard, joystick, printer data) / IC35 ($FF20, DAC, cassette, printer handshake, VDG mode) | Two 8-bit parallel ports with handshake lines. |
| Dragon 32 BASIC ROMs (MCM68A364) | IC17, IC18 | Microsoft Extended Color BASIC 1.0 for the Dragon, $8000–$BFFF in two 8 KB chips. |
| 4116 DRAM 16K x 1 | IC1-IC8 on the SA2120 sheet (16 chips: stacked on Siemens boards, two rows on 16x16 boards) | Dynamic RAM, 16K x 1 (lower 16K on the Spectrum) |
| MC14529B dual 4-channel analog data selector | IC20 | Joystick axis select for the A-to-D comparator, and sound source select for the TV and monitor. |
Ports and connectors
- Cartridge port, 40-pin card-edge socket UNVERIFIED
- Joystick ports (left PL5, right PL3), 5-pin DIN socket (240°)
- Cassette (TAPE, PL4), 5-pin DIN socket (180°)
- Parallel printer port (PL2), 20-pin (2 × 10) header, Centronics signals
- Monitor socket (PL11), 5-pin DIN socket (180°) UNVERIFIED
- TV (UHF RF out), Phono (RCA) socket on the modulator
- Power pack socket (PL9), 9-way D socket (pins 1-5 used)
- PSU board to CPU board (PL10 / PL6), 9-way board-to-board connector
- Keyboard connector (PL1), 16-way Molex header on the CPU board
Power rails
| Rail | Expect | Measure at |
|---|---|---|
| +5 V | +5 V | 6809E pin 7; SAM pin 40; 4116 pin 9 |
| +12 V | +12 V | 4116 pin 8; dragon-cart pin 1 (cartridge) |
| -5 V | -5 V | 4116 pin 1 |
| Raw | About +18 V and -18 V DC | LM7812 and LM7905 inputs on the PSU board |
Symptoms
- No picture and no sound: check SAM
- No sound, picture fine: check 4529 mux
- Bad or missing color: check VDG
- Garbage on screen: check BASIC ROM, SAM, 6809E
- Crashes while running programs: check SAM, BASIC ROM, 6809E, 4116
- Cassette will not load or save: check 4529 mux, 6821 PIA
- Joystick dead or reads full scale: check 4529 mux
- Cartridge will not start: check SAM, 6809E, 6821 PIA
- Printer prints nothing or garbage: check 6821 PIA
- RAM errors or 16K reported: check 4116, 6821 PIA