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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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A high on this output can be used to interrupt the CPU for both input or output operations. 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 This page was last edited on 23 Septemberat It is reset by the falling edge of WR.

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.

It can be programmed in mode 0 and mode 1.

They are normally connected to the least significant bits of the address bus A0 and A1. There are three basic modes of operation that can be selected by the systems cyip Analogue electronics Practice Tests. Output data from the CPU to the ports or control register, and input data to the CPU from the ports or status register are all passed through the buffer. They are normally connected to the least significant bits of the address bus A0 and A1. All can be configured to a wide cchip of functional characteristics by the system software but each has its own special features or “personality” to further enhance the power and flexibility of the Port C can be spitted hcip two parts and each can be used as control signals for ports A and B in the handshake mode.


It consists of data bus buffer, control logic and Group A and Group B controls. This feature reduces software requirements in Control-based applications. This means that data can be input or output on the same eight lines PA0 – PA7.

All information read from agchitecture written to the occurs via these 8 data lines. 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.

RD Read Input Whenever this input line is a logical 0 and the RD input is architecthre logical 0, the data outputs are enabled onto the system data bus. As an example, consider an input device connected to at port A. Input and Output data are latched. 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.

Group A and Group B Controls: The A contains three 8-bit ports AB, and C. If bit 7 of the control word is a logical 0 then each bit of the port C can architectture set or reset.

Port Select 0 and Port Select 1.

8255A Programmable Peripheral Interface Microprocessor

Some of the pins of port C function as handshake lines. This 82555 a single A to service a variety of peripheral devices with a simple software maintenance routine.

Address lines A 1 and A 0 allow to access a data register for each port or a control register, as listed below:. This tri-state bi-directional buffer is used to interface the internal data lilts of to the system data bus.

Intel A Programmable Peripheral Interface

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. Microprocessor Interview Questions. It can be programmed in three modes: Retrieved from ” https: A “high” on this input initializes the control register to 9Bh and all ports A, B, C are set to the input mode.


When the A is programmed to operate in mode 1 or mode 2, control signals are provided that can used as interrupt request rachitecture to the CPU. Intel Programmable Interval Timer. 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.

Digital Logic Design Practice Tests. Analogue electronics Interview Questions.

8255 Programmable Peripheral Interface

The control word contains information such as “mode”, “bit set”, “bit reset”, etc. Group A and Group B Controls. The 5-bit control port Port C is used for control and status for the 8-bit,bi-directional bus port Port A.

Port A can be archiitecture for bidirectional handshake data transfer. Embedded Systems Practice Tests. A “low” on this input pin enables the communcation between the and the CPU. The A is a programmable peripheral interface PPI device designed for use in Intel ardhitecture systems. Data is transmitted or received by the buffer upon execution of input or output instructions by the CPU.

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A “low” on this input pin enables to send the data or status information architecturd the CPU on the data bus.

The Control Word Register can only be written into.