C6845 Datasheet, PDF (1/6 Pages) List of Unclassifed Manufacturers – CRT Controller Megafunction

C6845
CRT Controller
Megafunction
General Description
The C6845 Cathode Ray Tube Controller (CRTC) interfaces a microprocessor to a raster-scan CRT display.
The C6845 is a synchronous, synthesizable VHDL megafunction, functionally equivalent to the Motorola
MC6845 CRT Controller.
The microprocessor access 19 registers (1 Address and 18 Data Registers) within the C6845 in order to
provide video timing, refresh memory addresses, cursor, and light pen strobe signals. CRT video timing signals
include Vertical Sync (VS), Horizontal Sync (HS), and Display Enable (DE) output signals. Refresh memory
addressing includes Memory Address (MA[13:0]) and Row Address (RA[4:0]) output buses.
The C6845 microprocessor interface consist of unidirectional data input (DIN[7:0]) and data output
(DOUT[7:0]) buses and control signals RS, RWn, CSn, and E. Optionally, an available bus wrapper converts
the unidirectional data buses into an 8-bit bi-directional data bus (D[7:0]). This is the pin equivalent to the
MC6845.
Features
• Fully-synchronous, synthesizable VHDL Megafunction, functionally equivalent to Motorola MC6845
• Capable of driving alphanumeric, semi-graphic, or bit-mapped graphics displays
• Wide range of programmable alphanumeric screen formats
• Programmable registers controlling output signals Vertical Sync (VS), Horizontal Sync (HS), and
Display Enable (DE) signals
• Programmable horizontal line rate and sync pulse width
• Programmable vertical frame rate
• Programmable registers controlling Memory Address (MA[13:0]) start address
• Programmable Start Address Register for Hardware Scrolling
• Programmable registers controlling Row Address (RA[4:0]) size, yielding a character row
• Programmable register controlling Normal Sync (Non-Interlace), Interlace Sync, or Interlace Sync &
Video Mode
• Programmable registers for control and format of Cursor
• Light Pen Register
• Microprocessor 8-bit Data Bus and Control Interface
CAST, Inc.
March 2004
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