input device with the output device or vice-versa. In order to make it simpler, Intel has designed A chip to interface I/O devices. The Intel A is a general. A Programmable Peripheral Interface in Microprocessor – A Programmable Peripheral The following figure shows the architecture of A −. The (or i) programmable peripheral interface (PPI) chip was developed and manufactured by Intel The PPI chip Architecture.

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Both Inputs and Outputs are latched. This mode is selected when Chp 7 bit of the Control Word Register is 1. Digital Communication Interview Questions.

Programmable Peripheral Interface

Otherwise, the output buffer will be in the high impedance state. Group A and Group B Controls: Rise in Demand for Talent Here’s how to train middle managers This is how banks are wooing startups Nokia to cut thousands of jobs. During the execution of the systems program any of the other modes may be selected using a single output Instruction.

Combination of MODE 1. Digital Logic Design Interview Questions.

In this mode, the may be used to extend the system bus to a slave microprocessor or to transfer data bytes to and from a floppy disk controller. A “low” on this input pin enables the CPU architexture write data or control words into the Control words and status information are also transferred through the data bus buffer.


8255A – Programmable Peripheral Interface

The functional configuration of each port is programmed by the systems software. A “high” on this input initializes the control register to 9Bh and all ports A, B, C are set to the input mode.

This is required because the data only stays on the bus for one cycle. The Control Word Register can only be written into. Analogue electronics Interview Questions. When we wish to use port A or port B for handshake strobed input or output operation, we initialise that port in mode 1 port A and port B can be initilalised to operate in different modes, i. When the A is programmed to operate in mode 1 or mode 2, control signals are provided that can used as interrupt request input to the CPU.

Explain with block diagram working of PPI. Computer architecture Interview Questions. Analogue electronics Architecyure Tests. Analog Communication Practice Tests. Port Select 0 and Port Select 1.

Intel A Programmable Peripheral Interface

Computer architecture Practice Tests. Intel Programmable Interval Timer.

It has the ability to use with almost any microprocessor. Each 4-bit port contains a 4-bit latch and it can be used for the control signal output and status signal inputs in conjunction with ports A and B. Port C can be spitted into two parts and each can be used as control signals for ports A and B in the handshake mode.


This page was last edited on 23 Septemberat Digital Electronics Interview Questions.

8255 Programmable Peripheral Interface

For instance; Group B can be programmed in Mode 0 to monitor simple switch closing or display computational results, Group A could be programmed in Mode 1 to monitor a keyboard or tape reader on an interrupt-driven basis.

Used in Group A only.

Inputs are not latched. This feature reduces software requirements in Control-based applications. The is also directly compatible with the Z, as well as many Intel processors. CS Chip Select Input. If bit 7 of the control word is a logical 0 then each bit of the port C can be set or reset.

The inputs are not latched because the CPU only has to read their current values, then store the data in a CPU register or memory if it needs to be referenced at a later time. Mode 1 Basic Functional Definitions: