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Motorola MC6845
1977
Motorola's widely used CRT controller, generating video timing for the IBM MDA/CGA, Amstrad CPC, BBC Micro and many terminals.
Machines
Emulators
| Emulator | Type | License | Site |
|---|---|---|---|
| B-em | downloadable | GPL-2.0 | Website ↗ |
| Sharp X1 | online | MIT | Website ↗ |
| b2 | downloadable | GPL-3.0 | Website ↗ |
| beebjit | downloadable | GPL-3.0 | Website ↗ |
| cpcjs | online | GPLv3 | Website ↗ |
Reference & documentation
External technical references for programming Motorola MC6845 and for writing emulators.
| Resource | Type | Notes |
|---|---|---|
| Motorola MC6845 CRTC Datasheet ↗ | Datasheet | Official 6845 CRTC datasheet: registers, pinout, timing. |
| Motorola MC6845 CRTC Reference ↗ | Pinout | Pin functions: data bus, MA/RA lines, sync signals |
| The 6845/6545 CRTC operation (6502.org) ↗ | Programming | Register programming, timing math, addressing modes |
| The Mighty CRTC 6845 (CPCRulez) ↗ | Programming | Counter/trigger model, variants, assembly examples |
| MC6845 CRTC Simplifies Video Displays (Motorola AN-0851) ↗ | Programming | Motorola app note on programming the 6845. |
| Motorola MC6845 CRTC Reference ↗ | Reference | Detailed walkthrough of all 18 CRTC registers |
| CRTC emulation for MESS (Reenigne) ↗ | Reference | Cycle-accurate emulation approach and variant differences |
| CGA 6845 CRTC Phantom VSync Glitch ↗ | Reference | R7 rewrite metastability quirk during active display |
| 6845 Quirks and FPGA implementation (stardot) ↗ | Reference | RVI, R0=1, end-of-frame latch, variant behaviors |
| floooh/chips mc6845.h emulator ↗ | Source | Header-only cycle-accurate C emulator for the MC6845 |