The Intel (or i) Programmable Peripheral Interface (PPI) chip was developed and .. 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. PPI is a general purpose programmable I/O device designed to by interfacing with microprocessor · I/O Interface (Interrupt and DMA Mode). Direct memory access with DMA controller / Step After accepting the DMA service request from the DMAC, the CPU will send hold Interface with microprocessor for 1’s and 2’s complement of a number · Parallel .

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Report Attrition rate dips in corporate India: 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.

Digital Communication Interview Questions. These are bidirectional, data lines which help to interface the system bus with the internal data bus of DMA controller. In the Slave mode, it carries command words to and status word from Analog Communication Practice Tests. In the master mode, it is used to load the data to the peripheral devices during DMA memory read cycle.

Intel 8255

How to design your resume? It is an active-low bidirectional tri-state input line, which is used by the CPU to read internal registers of in the Slave mode. This is required because the data only stays on the bus for one cycle. The two modes are selected on the basis of the value present at the D 7 bit of the control word register.


It is the hold acknowledgement signal which indicates the DMA controller that the bus has been granted to the requesting peripheral by the CPU when it is set to 1. Retrieved 3 June The is a member of the MCS Family of chips, designed by Intel for use with their and microprocessors and their descendants [1]. It is the low memory read signal, which is used to read the data from the addressed memory locations during DMA read cycles.

As an example, consider an input device connected to at port 8525.

8255A – Programmable Peripheral Interface

When we wish to use port A or port B for handshake strobed input or output operation, we initialise that contdoller in mode 1 port A and port B can be initilalised to operate in different modes, i.

It is designed by Intel to transfer data at the fastest rate.

The inputs are not latched because the CPU only has dmw read their current values, then store the data in a CPU register or memory if it needs to be referenced at a later time. Address lines A 1 and A 0 allow to access a data register for each port or a control register, as listed below:.

This signal helps to receive the hold request signal sent from the output device. Views Read Edit View history. These are the active-low and high inactive DMA acknowledge lines, which updates the peripheral requesting device service about the status of their request by the CPU.

It is an active-low bidirectional tri-state input line, which helps to read the internal registers of by the CPU in the Slave mode. It is specially designed by Intel for data transfer at the highest speed.


Since the two halves of port C are independent, they may be used such that one-half is initialized as an input port while the other half is initialized as an output port. It is the low memory read signal, which is used to read the data from the addressed memory locations during DMA read cycles.

Computer architecture Practice Tests. This signal is used to convert the higher byte of the memory address generated by the DMA controller into the latches.

Survey Most Productive year for Staffing: Have you ever lie on your resume? In the Slave mode, command words are carried to and status words from It is an active-high asynchronous input signal, which helps DMA 825 make ready by inserting wait states.

This page was last edited on cma Septemberat In the master mode, the lines which are used to send higher byte of the generated address are sent to the latch. 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.

Intel – Wikipedia

So, without latching, the outputs would become invalid as soon as the write cycle finishes. The functionality of the is now mostly embedded in larger VLSI processing chips as a sub-function. In the master mode, it also xontroller in reading the data from the peripheral devices during a memory write cycle.