April 8, 2021

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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Clears the display or FIFO. Output that blanks the displays. The display is controlled from an internal 16×8 RAM that stores the coded display information. Max is 3 MHz. Z selects auto-increment for the address. Interfacijg the number of display positions, type of key scan Chip select that enables programming, reading the keyboard, etc.


The output becomes a logic 0 when the control word is written and remains there until N plus the number of programmed counts. Strobed keyboard, encoded display scan. 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.

Programmable Keyboard/Display Interface –

SL outputs are active-low only one low at any time. The previous example illustrates an encoded keyboard, external decoder used to drive matrix.

DD field selects either: Keyboard Interface of MMM field: Usually decoded at port address 40HH and has following functions: 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: Scan line outputs scan both the keyboard and displays.

Generates a continuous square-wave with G set to 1. An events counter enabled with G.

Microprocessor – I/O Interfacing Overview

Provides a timing source to the internal speaker and other devices. Interrupts the micro at interrupt vector 8 for a clock tick.

Interfcing scans RL pins synchronously with the scan. Encoded keyboard with 2-key lockout. The first 3 bits of sent to control port selects one of 8 control words.


vhip MMM sets keyboard mode. Selects type of display read and address of the read. The 74LS drives 0’s on one line at a time. Strobed keyboard, decoded display scan.

DD Function 00 8-digit display with left entry 01 digit display with left entry 10 8-digit display with right entry 11 digit display with right entry. Interface of WWBB The display write inhibit control word inhibits writing to either the leftmost 4 bits of the display left W or rightmost 4 bits.

Once done, a procedure is needed to read data from the keyboard. Six Digit Display Interface of interfaacing Keyboard Interface of First three bits given below select one of 8 control registers opcode. To determine if a character has been typed, hcip FIFO status register is checked. Pinout Definition A0: