Motorola MC6809 connection guide
Motorola MC6809 MC6809 DIP-40 wiring guide with power, signal assignments, and bench checks.
MC6809 DIP-40
40 contacts Current package2.0 MHz maximum bus rate. MC68B09P/S/L (0–70 °C) and MC68B09CP/CS/CL (−40 to +85 °C).
5 V supply and bypass
RequiredApply regulated 5 V and fit a 100 nF ceramic bypass with short connections to the supply rails.
Bench checks
- Verify pin 1 is grounded and measure 4.75–5.25 V at pin 7.
- Keep RESET asserted during supply and clock startup. The bypass capacitor is a board-level design choice.
Motorola MC6809 datasheet DS9845-R2, pp. 1–2
Connection scenarios
4 MHz crystal clock
Use a 4 MHz parallel-resonant crystal and the 24 pF load capacitors from Motorola’s example for 1 MHz bus operation. Use the crystal parameters from Fig. 7 and account for board stray capacitance.
- Oscillator input
- EXTAL (38)
- Y1.1
- C2.1
- Oscillator return
- XTAL (39)
- Y1.2
- C3.1
- Reference
- VSS (1)
- C2.2
- C3.2
- Oscilloscope GND
- Bus clock probe
- E (34)
- Oscilloscope CH1
Bench checks
- Keep the crystal and both capacitors near pins 38 and 39. Use 24 pF C0G capacitors for the reference circuit.
- Keep RESET low through oscillator startup. The bus timing table allows up to 100 ms oscillator start time.
- Check for 1 MHz on E using a high-impedance probe. A probe on the crystal nodes can alter oscillator loading.
Motorola MC6809 datasheet DS9845-R2, Figs. 6–7 and bus timing table
MC6809 DIP-40 wiring map
33 · /DMA/BREQ
Low requests temporary bus ownership. Observe BA and BS and allow for automatic CPU self-refresh cycles. Keep high when unused.
Models and documents
Covers the Motorola MC6809 and MC6809E plus their A and B speed grades. On the MC6809, E and Q are outputs. On the MC6809E, both are inputs, and pins 33, 36, 38 and 39 also differ. Hitachi HD6309 and later CMOS versions require their own datasheets.
- MC6809
- 1.0 MHz maximum bus rate. MC6809P/S/L (0–70 °C) and MC6809CP/CS/CL (−40 to +85 °C).
- MC68A09
- 1.5 MHz maximum bus rate. MC68A09P/S/L (0–70 °C) and MC68A09CP/CS/CL (−40 to +85 °C).
- MC68B09
- 2.0 MHz maximum bus rate. MC68B09P/S/L (0–70 °C) and MC68B09CP/CS/CL (−40 to +85 °C).
- Motorola MC6809 datasheet DS9845-R2· Manufacturer scan, © 1983. Pin map p. 1, electrical and bus timing pp. 2–3, crystal and reset pp. 7–8, ordering p. 35. Scan SHA-256 87037123596de83bbc44ac63fbcde3950d368d5ee30880bffaa54e23bb81ea68.
- Motorola MC6809E datasheet DS9846-R2· Manufacturer scan, © 1984. Check the pin assignment, external clock thresholds and timing, TSC timing and ordering table. Scan SHA-256 42c50598f2184bc37535a8d59be60a895c14e34919d706317b18f02f73441808.
- Motorola MC6809–MC6809E Microprocessor Programming Manual· Programming model, interrupt handling and vectors. Appendix B lists the two pin assignments side by side.