Motorola MC6845 Manual

Advance Information
CRT CONTROLLER (CRTC)
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 stand·alone 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, RIW, cursor movements, and editing
are under processor control; whereas the CRTC provides video timing
and Refresh Memory Addressing.
• Applications include "glass-teletype," smart, programmable, intel-
ligent 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.
• Prograli'lli'lable interlace or non-interlace scan.
• 14-bit wide refresh address.
MC6845
MOS
(N-Channel, Silicon-Gate)
CRT CONTROLLER
(CRTC)
CERAMIC PACKAGE
CASE 715
NOT SHOWN;
P SUFFIX
PLASTIC PACKAGE
CASE 711
FIGURE 1 - TYPICAL CRT CONTROLLER APPLICATION
Processor
r
t
s
L.,
High Speed
CLK
Refresh
~
CRTC MUX
r-.
Timing
..",
RAM
,
I
Refresh
Memory
Addresses
~
Light
~
Pen f---
Circuit
Row Addresses
.."
,
,
H Sync V Sync
This is advance information and specifications are subject to change without notice.
-
AB
..
OB
t
s
Secondary
Bus
-""
3·State
Buffer
-
Latch
r
ROM
~
Shift
Character
Registor
Generator
@MOTOROLA INC. 1977
Primary Bus
Cursor,
Display
Enable
~
Video
~
Output
A01·465
(Replaces NP·67)