From The Dragon Archive

The MC6845 CRT Controller performs the interface to raster scan CRT displays. It is intended for use in processor-based controllers for CRT terminals in standalone or cluster configurations. The CRTC is optimized for hardware/software balance in order to achieve integration of all key functions and maintain flexibility. For instance, all keyboard functions, R/W, cursor movements, and editing are under processor control; whereas the CRTC provides video timing and Refresh Memory Addressing.

• Applications include "glass-teletype," smart, programmable, intelligent CRT terminals; video games; information display.

• Alphanumeric, semi-graphic, and full graphic capability.

• Fully programmable via processor data bus. Can generate timing for almost any alphanumeric screen density, e.g. 80 x 24, 72 x 64,132 x 20, etc.

• Single +5 volt supply. TTL/6800 compatible I/O.

• Hardware scroll (paging or by line or by character).

• Compatible with CPU's and MPU's which provide a means for synchronizing external devices.

• Cursor register and compare circuitry.

• Cursor format and blink are programmable.

• Light pen register.

• Line buffer-less operation. No external DMA required. Refresh Memory is multiplexed between CRTC and MPU.

• Programmable Interlace or non-interlace scan.

• 14-bit wide refresh address