Dragon 64
A Dragon 32 with 64 KB, a second BASIC ROM and a 6551 RS-232 port.
Open the Dragon 64 in Retro Bench- Also
- Dragon 200 (Eurohard, Spain) is the same board; the Tano Dragon is the US NTSC Dragon 64
- Year
- 1983
- CPU
- 6809E @ 0.89 MHz
- RAM
- 64 KB (8 × 4164)
- ROM
- 2 × 16 KB BASIC (HN613128P): Dragon 32 mode and 64K mode, switched by PB2 of $FF22
- Video
- MC6847 VDG, PAL (NTSC on the Tano)
- Sound
- 6-bit DAC and single-bit sound from the $FF20 PIA, through the 4529 mux
- OS
- Microsoft Extended Color BASIC; 64K mode BASIC runs from RAM
Chips
| Chip | Where | Role |
|---|---|---|
| MC6883 synchronous address multiplexer | IC39 (74LS783) | Makes all clocks from the 14.31818 MHz crystal, the DRAM strobes and address multiplex, and the device selects. Used in the CoCo 1 and 2 and the Dragon 32 and 64. |
| MC6809E microprocessor | IC38 (6809EP) | Main CPU, 8-bit with 16-bit registers. Same CPU in every CoCo and in the Dragon 32 and 64. |
| MC6847 video display generator | IC10 | Text, semigraphics and color video from screen RAM. Used in the CoCo 1 and 2, the MC-10 and the Dragon 32 and 64. |
| MC6821 peripheral interface adapter | IC5 ($FF00) / IC8 ($FF20) | Two 8-bit parallel ports with handshake lines. |
| 6551 ACIA | IC11 (SY6551, $FF04-$FF07) | RS-232 serial (Plus/4 only) |
| Dragon 64 BASIC ROMs (HN613128P) | IC34 (ROM 1), IC37 (ROM 2) | ROM 1: Dragon 32-compatible BASIC at $8000–$BFFF. ROM 2: the 64K-mode BASIC that the boot copies into RAM. |
| 4164 DRAM 64K×1 | IC15, IC16, IC21, IC22, IC26, IC27, IC32, IC33 | Main RAM (8 chips = 64 KB) |
| MC14529B dual 4-channel analog data selector | IC6 | Joystick axis select for the A-to-D comparator, and sound source select for the TV and monitor. |
Ports and connectors
- Cartridge port (PL7), 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
- RS-232 serial (PL8), 7-pin DIN socket (270°)
- Monitor socket (PL11), 5-pin DIN socket (180°)
- TV (UHF RF out), Phono (RCA) socket on the modulator
- Power pack socket (PL9), 9-way D socket
- 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; 4164 pin 8; 6551 pin 15 |
| +12 V | +12 V | dragon-cart pin 1 (cartridge); dragon-serial pin 3 (PL8, through 4.7 kΩ) |
| -12 V | -12 V | dragon64-psu pin 3 (PL6); dragon-serial pin 7 (PL8, through 4.7 kΩ) |
| -5 V | -5 V UNVERIFIED | 79L05 output on the CPU board |
Symptoms
- No picture and no sound: check SAM
- No sound, picture fine: check 4529 mux
- Garbage on screen or crashes: check BASIC ROM, SAM, 6809E, 4164
- EXEC will not enter 64K mode: check BASIC ROM, 6821 PIA, 4164
- No RS-232: check 6551
- Cassette or joystick faults: check 4529 mux, 6821 PIA
- Printer faults: check 6821 PIA