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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Embedded C Interview Questions. Combination of MODE 1.

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. Jobs in Meghalaya Jobs in Shillong.

All Mask flip-flops are automatically reset 2855 mode selection and device reset. There are three basic modes of operation that can be selected by the systems software: The A contains three 8-bit ports AB, and C.

8255A Programmable Peripheral Interface Microprocessor

In essence, a response from the peripheral device indicating that it has received the data output by CPU. Some of the pins of port C function as handshake lines. The functionality of the is now mostly embedded in larger VLSI processing chips as a sub-function.

Mode 1 Basic Functional Definitions: Digital Logic Design Interview Questions. The two halves of port C can be either used together as an additional 8-bit port, or they can be used as individual 4-bit ports. They are normally connected to the least significant bits of the address bus A0 and A1.

This 3-stable bi-directional 8-bit buffer is used to interface the A to the systems data bus. This page was last edited on 23 Septemberat The is also directly compatible with the Z, as well as many Intel processors. This feature reduces software requirements in Control-based applications. Port Select 0 and Port Select 1. 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. Data is transmitted or received by the buffer upon execution of input or output instructions by the CPU.


WR Write Input Whenever this input line is a logical 0 and the CS input is a logical 0, data is written to the from the system data bus A0 – A1 Address Inputs The logical combination of these two input lines determines which internal register of the data is written to or read from.

Intel – Wikipedia

Digital Electronics Practice Tests. 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 architectute later time. Figure shows the internal block diagram of A. Analog Communication Interview Questions.

The ‘s outputs are latched to hold the last data written to them. This is required because the data only stays on the bus for one cycle. Retrieved 3 June 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.

Engineering in your pocket Chjp our mobile app and study on-the-go. A “high” on this input cchip the control register to 9Bh and all ports A, B, C are set to the input mode. A high on this output can be used to architefture the CPU for both input or output operations. After the reset is removed the A can remain in the input mode with no additional Initialization required.

Intel A Programmable Peripheral Interface

The control logic block accepts control bus signals as well as inputs from the address bus, and issues commands to the individual group control blocks Group A control and Group B control. All of the output registers, including the status flip-flops, will be reset whenever the mode is changed. Analogue electronics Interview Questions. The A is generally seen as 8-bit bidirectional data buffer, which is specially designed to transfer the data with the execution of input output instructions requested by the CPU.


If this line is a logical 0, the microprocessor can read and write to the Digital Communication Interview Questions.

Intel 8255

Group A and Group B Controls: This allows a single A to service a variety of peripheral devices with a simple software maintenance routine. It can be programmed in mode 0 and mode 1.

This mode is selected when D 7 bit of the Control Word Register is 1. Microprocessor Interview Questions. Two 8-bit ports and two 4-bit port Any port can be input or output.

Definition of Microprocessor 1. If an input changes while the port is being read then the result may be indeterminate. These three ports are further classified into two groups, i. This port can be divided architechure two 4-bit ports under the mode control. Mode 2 — Bi-Directional Bus. Control words and status information are also transferred through the data bus buffer.

Report Attrition rate dips in corporate India: They can be connected to peripheral devices. The i was also used with the Intel and Intel [1] and their descendants and found wide applicability in digital processing systems.