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.

Author: Fenrir Mit
Country: Greece
Language: English (Spanish)
Genre: Love
Published (Last): 5 February 2010
Pages: 418
PDF File Size: 14.94 Mb
ePub File Size: 14.71 Mb
ISBN: 882-6-81775-159-7
Downloads: 25022
Price: Free* [*Free Regsitration Required]
Uploader: Shagis

A BSR word is written for each bit Programmaable DD sets displays mode. Encoded keyboard with N-key rollover. Generates a basic timer interrupt that occurs at approximately 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.

In this modetwo 8 bit ports port A and port B and two 4 bit ports port C upper and port C lower are available. Usually decoded at port address 40HH and has following functions: Any port can be used as an input or output port. Report Attrition rate dips in corporate India: This mode deals with display-related operations. Shift connects to Shift key on keyboard. About project SlidePlayer Terms of Service. The output becomes a logic 0 when the control word is written and remains there until N plus the number of programmed counts.

The keyboard consists of maximum 64 keys, which are interfaced with the CPU by using the key-codes.

These lines can be programmed as encoded or decoded, using the mode control register. Jobs in Meghalaya Jobs in Shillong.


With the help of keyboard the user can perform various types of tasks. Read This Tips for writing resume in slowdown What do employers look for in a resume? SL outputs are active-high, follow binary bit pattern or depending on 8 or 16 digit display.

This unit contains registers which stores the keyboard, display modes, and other operations that are programmed by the CPU. Microprocessor Interview Questions. Used for controlling real-time events such as real-time clock, events counter, and motor speed and direction control.

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.

Microprocessor – Programmable Keyboard

This mode deals with display-related operations. Keyboard Interface of Published by Jaidyn Tea Modified over 3 years ago. As mentioned earlier these lines can be programmed as encoded or decoded, using the mode control register. The display can be blanked by BD low line.

In decoded scan mode, the output of scan lines will be similar to a 2-to-4 decoder. Ramadan Al-Azhar University Lecture 3.


DD Function Encoded keyboard with 2-key lockout Decoded keyboard with 2-key lockout Encoded keyboard with N-key rollover Decoded keyboard with N-key rollover Encoded sensor matrix Decoded sensor matrix Strobed keyboard, encoded display scan Strobed keyboard, decoded display scan Encoded: The 8 bit data port can be either used as input or output port.

The main function is to act as an interface with the CPU with the help of these key-codes. Interface of 2 Keyboard type is programmed next. Each counter has a program control word used to select the progammable the counter operates.



It is a programmable device. It has two modes i.

Features of The important features of programamble, Simultaneous keyboard and display operations. Z selects auto-increment so subsequent writes go to subsequent display positions. The previous example illustrates an encoded keyboard, external decoder used to drive matrix.

8279 – Programmable Keyboard

Chip select that enables programming, reading the keyboard, etc. Shift connects to Shift key on keyboard. Share buttons are a little bit lower. In the Polled mode, the CPU periodically reads an internal flag of and checks whether any key is pressed or not with any pressure exerted by the key.

The cathodes are connected to scan lines through driver transistors. This unit which has buffers, keyboard debounce etc first scans the key that is close in row-wise, if found then the keyboard debounce unit debounces the pefipheral entry.

In the Interrupt modethe processor is requested service only if any key is pressed, otherwise the CPU will continue with its main task. 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. When it is low, it indicates the transfer of data. This is used periphetal reset the device.