INTERFACING OF WITH In a microprocessor b system, when keyboard and 7-segment LED display is interfaced using ports or latches then the . User Manual for Keyboard and Display Interface Card. Hardware Configuration of With // a) Interface With Interfacing Keyboard Controller with Aparatus. 1. Microprocessor toolkit. 2. Interface board. 3. VXT parallel bus. 4. Regulated D.C power.

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Register Architecture of Microprocessor.

8279 – Programmable Keyboard

In the Polled modethe CPU periodically reads an internal flag of to check whether any key is pressed or not with key pressure. These lines are wlth to 0 when any key is pressed. The Keyboard can be interfaced either in the interrupt or the polled mode.

This mode deals with the input given by the keyboard and this mode is further classified into 3 modes. It has two modes i. Till it is pulled low with a key closure, it is pulled up internally to keep it high.

It has an internal pull up. Its data buffer interfaces the external bus of the system with the internal bus of the microprocessor.


CLK input of is driven from the clock out of Reset out signal from is connected to the Reset signal of the In the encoded mode, the counter provides the binary count that is to be externally decoded to provide the scan lines for the keyboard and display. To get absolute address, all remaining address lines A 2 -A 19 are used to decode the address for It is enabled only when D is low.

This unit controls the flow of data through the microprocessor. Operating Modes of The line is pulled down with a key closure.


These are the scan lines used to scan the keyboard matrix and display the digits. Encoded mode and Decoded mode. It then sends their relative response of the pressed key to the CPU and vice-a-versa. This unit contains registers to store the keyboard, display modes, and other operations as programmed by the CPU.

Timers and Counters in Microcontroller.

The timing and control unit handles the timings for the operation of the circuit. These are the Return Lines which are connected to one terminal of keys, while the other terminal of the keys is connected to the decoded scan lines.


These are the output ports for two 16×4 or one 16×8 internal display refresh registers. Interrupt signal from the is connected to the interrupt input of Conditional Statement in Assembly Language Program. Intel CPU Structure. In the keyboard mode, this line is used as a control input and stored in FIFO on a key closure.

Features of DMA Controller. Leave a Reply Cancel reply Your email address will not be published. Speed Control of DC Motor.

Interfacing of with This is when the overrun status is set. This mode deals with display-related operations. If more interfcing 8 characters are entered sith the FIFO, then it means more than eight keys are pressed at a time.

When it is low, it indicates the transfer of data. The keyboard first scans the keyboard and identifies if any key has been pressed. The chip select signal, CS is generated using decoding circuit.