8279 interfacing with Processor :
Pin Diagram of 8279 :
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| fig.Pin Diagram of IC 8279 |
It is 40 pin IC ,
- A0: Selects data (0) or control/status (1) for reads and writes between micro and 8279.
- BD: Output that blanks the displays.
- CLK: Used internally for timing. Max is 3 MHz.
- CN/ST: Control/strobe, connected to the control key on the keyboard.
- CS: Chip select that enables programming, reading the keyboard, etc.
- DB7-DB0: Consists of bidirectional pins that connect to data bus on micro.
- IRQ: Interrupt request, becomes 1 when a key is pressed, data is available.
- OUT A3-A0/B3-B0: Outputs that sends data to the most significant/least significant nibble of display.
- RD(WR): Connects to micro's IORC or RD signal, reads data/status registers.
- RESET: Connects to system RESET.
- RL7-RL0: Return lines are inputs used to sense key depression in the keyboard matrix.
- Shift: Shift connects to Shift key on keyboard.
- SL3-SL0: Scan line outputs scan both the keyboard and displays.
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