Description: The NTE input/output port is an integrated circuit in a 24–Lead DIP type package and consists of an 8–bit latch with three–state output buffers. Computer interfacing has traditionally been an art, the art to design and implement the Microprocessor interface-chips have not reached their maturity yet. They are still “dumb” chips. System Controller Using and ‘s. Control or. After a delay, call it to/-, chip 1 data outputs again enter the float state. Example In Example , we developed a decoding circuit for interfacing EPROM within the memory chips, we have used the latch in Fig to latch this byte.

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Microprocessor I/O Interfacing Overview

There are 6 modes of operation for each counter: Controls up to a digit numerical display. The display is controlled from an internal 16×8 RAM that stores the coded display information.


Unlike the 82C55, the must be programmed first. Keyboard has a interfacig FIFO 8 character buffer. The address inputs select one of the four internal registers with the as follows: Selects the number of display positions, type of key scan Decoded keyboard with N-key rollover.

Allows half-bytes to be blanked. Six Digit Display Interface of Strobed keyboard, decoded display scan.

BB works similarly except that they blank turn off half of the output pins. 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.

Microprocessor – I/O Interfacing Overview

The output becomes knterfacing logic 0 when the control word is written and remains there until N plus the number of programmed counts. DD field selects either: Shift connects to Shift key on keyboard. Used for controlling real-time events such as real-time clock, events counter, and motor speed and direction control.

An events counter enabled with G. Each counter has a program control word used to select the way chup counter operates.


Keyboard Interface of MMM field: Output that blanks the displays. Programs internal clk, sets scan and debounce times. The scans RL pins synchronously with the scan. Encoded keyboard with N-key rollover. Decoded keyboard with 2-key lockout. Pins SL2-SL0 sequentially scan each column through a counting operation. Selects type of display read and address interafcing the read.

Programmable Keyboard/Display Interface –

Sl outputs are active-high, follow binary bit pattern or Interface of Code given in text for reading keyboard. DD sets displays mode.

Usually decoded at port address 40HH and has following functions: Interrupts the micro at interrupt vector 8 for a clock tick.

MMM sets keyboard mode. Interface of 2 Keyboard type is programmed next. Z selects interfacinb for the address.

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