The INTEL is specially developed for interfacing keyboard and display Programmable scan timing. The functional block diagram of is shown. It is a specially designed type of programmable keyboard/display controller launched by Intel which helps in interfacing the keyboard with the CPU. It identifies. 3 Function of pins: Data bus(D0-D7):These are 8-bit bi-directional buses, connected to data bus for transferring data. CS: This is Active Low signal. When it.

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The main function is to act as an interface with the CPU with the help of these key-codes. Shift connects to Shift key on keyboard. Embedded C Interview Questions.

The output lines can be used either as a single group of eight lines or as two groups of four lines, in conjunction with the scan lines for a multiplexed display. A BSR word is written for ptogrammable bit Example: Consists of bidirectional pins that connect to data bus on micro. Registration Forgot your password?

Its data buffer interfaces the external bus of the system with the internal bus of the microprocessor. This unit which has buffers, keyboard debounce etc first scans the key that is close in row-wise, if periheral then the keyboard debounce unit debounces the key entry. Microprocessor Interview Questions. We think you have liked this presentation.



In encoded scan mode, the output of scan lines will be binary count, and interrace an external decoder should be used to convert the binary count to decoded output. When it is low, then data is transfer from Report Attrition rate dips in inteface India: If two bytes are programmed, then the first byte LSB stops the count, and the second byte MSB starts the counter with the new count.

Programs internal clk, sets scan and debounce times. The line is pulled down with a key closure. This unit first scans the key closure row-wise, if found then the keyboard debounce unit debounces the key entry. Any port can be used as an input or output port. Certain specific progtammable are used where text is entered as an input with the keyboard. Analog Communication Interview Questions.

The keyboard which acts as an input device contains maximum of 64 keys.

8279 Programmable Keyboard Microprocessor

Minimum count is 1 all modes except 2 and 3 with minimum count of 2. In the scanned sensor matrix mode, this unit acts as sensor RAM where its each row is loaded with the status of their corresponding row of sensors into the matrix.


It has an interrupt request line IRQ, for interrupt driven data transfer with processor. The display is controlled from an internal 16×8 RAM that stores the coded display information. In the Interrupt mode, whenever any key is pressed then interfaec request is sent by the processor, otherwise the CPU will continue to follow with its main task. It can be programmed by mode 0mode 1, mode 2. Output that blanks the displays.

Read This Tips for writing resume in slowdown What do employers look for in a resume? This unit controls the data flow through the microprocessor. Used internally for timing.

If more than 8 characters are entered in the Perpiheral, then it means more than eight keys are pressed at a time. These are the scan lines which help to scan the keyboard matrix and display the digits.

Max is 3 MHz.

DD field selects either: These lines are set to 0 when any key is pressed. Usually decoded at port address 40HH and has following functions: