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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Figure shows the internal block diagram of A.

All Mask flip-flops are automatically reset during mode selection and device reset. If from the previous operation, port A is initialized as an output port and if is not reset before using the current configuration, then there is a possibility of damage of either the input device connected or or both, since both and the device connected will be sending out data.

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. Views Read Edit View history. There are three basic modes vhip operation that can be selected by the systems software: All of the output registers, including the status flip-flops, will be reset whenever the mode is changed. This has an 8-bit latched and buffered output and an 8-bit input latch.


Explain with block diagram qrchitecture of PPI.

Group A and Group B Controls. Both “pull-up” and “pull-down” bus-hold devices are present on Port A. Retrieved 3 June Bit definitions of the control register to modify single bits of port C. The A is a programmable peripheral interface PPI device designed for use in Intel microcomputer systems.

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

This port can be divided into two 4-bit ports under the mode control. Embedded Systems Practice Tests. 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. Address lines A 1 and A 0 allow to access a data register for each port or a control register, as listed below:. Interrupt logic is supported.

Input and Output data are latched.

If bit 7 of the control word is a logical 0 then each bit of the port C can be set or reset. 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.

Intel 8255

Some of the pins of port C function as handshake lines. The ‘s outputs are latched to hold the last data written to them. 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. Outputs are not latched. Mode 1 Basic Functional Definitions: The Control Word Register can only be written into. Data is transmitted or received architectude the buffer upon execution of input or output instructions by the CPU.


So, without latching, the outputs would become invalid as soon as the write cycle finishes. Control words and status information are also transferred through the data bus buffer.

8255 Programmable Peripheral Interface

The functional configuration of chiip A is programmed by the systems software so that normally no external logic is necessary to interface peripheral devices or structures.

Microprocessor And Its Applications. 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. Mode O Basic Functional Definitions: Tutorial of Microprocessor, assembly etc. Two 8-bit ports and two 4-bit port Any port can be input or output. Port A can be used for bidirectional handshake data transfer.

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