HD6845SP Renesas Electronics America, HD6845SP Datasheet - Page 4

• Manufacturer Part Number: HD6845SP
• Description: CRT Controller
• Manufacturer: Renesas Electronics America

Specifications of HD6845SP

• Power Supply Type: Analog
• Typical Operating Supply Voltage: 5 V
• Minimum Operating Supply Voltage: 4.75 V
• Maximum Operating Supply Voltage: 5.25 V

Enable signal (E) is used as strobe signal in MPU Read/Write operation with the CRTC internal registers. This signal is
normally a derivative of the HD6800 System Ø, clock.
Reset (/RES)
Reset Signal (/RES) is an input signal used to reset the CRTC. When /RES is at "low" level, it forces the CRTC into the
following status:
This signal is different from other HD6800 family LSIs in the following functions and has restrictions for usage:
* Interface Signals to CRT Display Device
Character Clock (CLK)
Input Pin No. 21
CLK is a standard clock input signal which defines character timing for the CRT display operation. CLK is normally
derived from the external high-speed dot timing logic.
Horizontal Sync (HSYNC)
Output Pin No. 39
HSYNC is an active "high" level signal which provides horizontal syncronization for display device.
Vertical Sync (VSYNC)
Output Pin No. 40
VSYNC is an active "high" level signal which provides vertical sychronization for display device.
Display Timing (DISPTMG)
Output Pin No. 18
DISPTMG is an active "High" level signal which defines the display period in horizontal and vertical raster scanning. It is
necessary to enable video signal only when DISPTMG is at "High" level.
Refresh Memory Address (MA0-MA13)
Output Pin. No 4-17
Hitachi HD6845 Cathode Ray Tube Controller
http://andercheran.aiind.upv.es/~amstrad/docs/hd6845s/hd6845sp.htm (4 of 20)4/15/2004 11:36:03 AM
All the counters in the CRTC are cleared and the device stops the display operation
All the outputs go down to "low" level.
Control registers in the CRTC are not affected and remain unchanged.
/RES has capability of reset function only when LPSTB is at "low" level.
The CRTC starts the display operation immediatly after /RES goes "high" level.