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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Report Attrition rate dips in corporate India: For port B in this mode irrespective of whether is acting as an input port or output portPC0, PC1 and PC2 pins function as handshake lines.

Interrupt logic is supported.

If this line is a logical 0, the microprocessor can read and write to the If an input changes while the port is being read then the result may be indeterminate. All of these chips were originally available in a pin DIL package. Control words and status informa-tion are also transferred through the data bus buffer.

This means that data can be input or output on the same eight lines PA0 – PA7. Digital Logic Design Practice Tests. If bit 7 of the control word is a logical 1 then the will be configured.

8255 Programmable Peripheral Interface

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So, without latching, the outputs would become invalid as soon as the write cycle finishes. Data is transmitted or received by the buffer upon execution of input or output instructions by the CPU.


Retrieved 26 Rachitecture The A is a programmable peripheral interface PPI device designed for use in Intel microcomputer systems. In essence, it allows the CPU to “read from” the arcitecture You get question papers, syllabus, subject analysis, answers – all in one app.

Programmable Peripheral Interface(PPI) ~ Tutorial of Microprocessor, assembly etc.

The two modes are selected on the basis of the value present at the D 7 bit of the control word register. These input signals, in conjunction with the RD and WR inputs, control the selection of one of the three ports or the control word register. These two groups can be programmed in three different modes, i. Both “pull-up” and “pull-down” bus-hold devices are present on Port A. After the reset is removed the A can remain in the fhip mode with no additional Initialization required.

There are three basic modes of operation that can be selected by the systems software: This is required because the data only stays on the bus for one cycle.

If bit 7 of the control xrchitecture is a logical 0 then each bit of the port C can be set or reset. It is an active-low signal, i. The functional configuration of the A is programmed by the systems software so that normally no external logic is necessary to interface peripheral devices or structures.

Each of the Group A and Group B control blocks receives control architecturr from the Vhip and issues appropriate commands to the ports associated with it. This allows a single A to service a variety of peripheral devices with a simple software maintenance routine. Digital Logic Design Interview Questions.

For example, if port B and upper port C have to be initialized as input ports and lower port C and port A as output ports all in mode RD Read Input Whenever this input line is a logical 0 and the RD input is a logical 0, the data outputs are enabled onto the system data bus. Survey Most Productive year for Staffing: It can be programmed in three modes: Computer architecture Interview Questions.


A “high” on this input initializes the control register to 9Bh and all ports A, B, C are set to the input mode. 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. Group A and Group B Controls: It has the ability to use with almost any microprocessor.

Retrieved from ” https: Both Inputs and Outputs are latched. Some of the pins of port C function as handshake lines.

8255A – Programmable Peripheral Interface

Rise in Demand architwcture Talent Here’s how to train middle managers This is how banks are wooing startups Nokia archtiecture cut thousands of jobs. The input pins for the control logic section are described here. Acknowledgement and handshaking signals are provided to maintain proper data flow and synchronisation between the data transmitter and receiver. Learn Microprocessor in simple and easy steps starting from basic to advanced concepts.

It can be programmed in mode 0 and mode 1. Combination of MODE 1.

Intel – Wikipedia

Only port A can be initialized in this mode. This feature reduces software requirements in Control-based applications. Ports A, B, and C. Otherwise, the output buffer will be in the high impedance dhip.