Control Word is an instruction or command send to to set its ports or pins as input, output or interrupt driven. It is used with many microprocessors and microcontrollers for various purposes. The device has three 8-bit ports port A, port B and port C. These ports can be used as input or output. These ports are further divided in to two groups A and B.

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We can program it according to the given condition. It can be used with almost any microprocessor. We can assign different ports as input or output functions. Port C is further divided into two 4-bit ports i.

Port B can work in either mode or in mode 1 of input-output mode. Port A can work either in mode 0, mode 1 or mode 2 of input-output mode. It has two control groups, control group A and control group B. Control group A consist of port A and port C upper. Control group B consists of port C lower and port B.

This is done by writing a suitable word in control register control word D0-D7. Example: A CPU wants to transfer data to a printer. In this case since speed of processor is very fast as compared to relatively slow printer, so before actual data transfer it will send handshake signals to the printer for synchronization of the speed of the CPU and the peripherals.

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AFM 36-2203 PDF

Intel 8255

The Intel or i Programmable Peripheral Interface PPI chip was developed and manufactured by Intel in the first half of the s for the Intel microprocessor. The is a member of the MCS Family of chips, designed by Intel for use with their and microprocessors and their descendants. The functionality of the is now mostly embedded in larger VLSI processing chips as a sub-function. All of these chips were originally available in a pin DIL package. Address lines A 1 and A 0 allow to access a data register for each port or a control register, as listed below:. It is an active-low signal, i.


8255A Programmable Peripheral Interface Pinout and Working



Programmable peripheral interface 8255


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