The three ports are Port A, Port B and Port C and as each port has 8 lines, but the 8 bits of port C is divided into 2 groups of 4-bit each. These are given as port C lower i. And are arranged in group of 12 pins each thus designated as Group A and Group B. The other mode of i. This means if is programmed to mode 1 input, then it will particularly be connected to an input device and performs the input handshaking with the processor. But if it is programmed to mode 2 then due to bidirectional nature, the PPI will perform both input and output operation with the processor according to the command received.

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Fenricage 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. 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. Each line of port C PC 7 — PC 0 can be set or reset by writing a suitable value to the control word register.

From Wikipedia, the free encyclopedia. Group A and Group B Controls. Output data from the CPU to the pli or control register, and input data to the CPU from the ports or status register are all passed through the buffer.

Only port A can be initialized in this mode. Digital Electronics Practice Tests. Retrieved 26 July Used in Arhcitecture A only. How to design adchitecture resume? Combination of MODE 1. The is also directly compatible with the Z, as well as many Intel processors. Figure shows the internal block diagram of A. All Mask flip-flops are automatically reset during mode selection and device reset.

The inputs are not latched because the Pppi only has to read their current values, then store the data in a CPU register or memory if it needs to be referenced at a later time. All peripheral ports are set to the input mode. Tutorial of Microprocessor, assembly etc. If an pi changes while the port is being read then the result may be indeterminate. This feature reduces software requirements in Control-based applications.

Outputs are not latched. Acknowledgement and handshaking signals are provided to maintain proper data flow and synchronisation between the data transmitter and receiver.

These three ports are further classified into two groups, i. Intel — Wikipedia Analogue electronics Practice Tests.

The is a member of the MCS Family of chips, designed by Intel for use with their and microprocessors and their descendants [1]. This mode is selected when D 7 bit of the Control Word Register is 1. It is an active-low signal, i. All of the output registers, including the status flip-flops, will be reset whenever the mode is changed.

It is reset by the falling edge of WR. If bit 7 of the control word is a logical 1 then the will be configured. Arfhitecture 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.

The Input signals, in conjunction with the RD and WR Inputs, controls the selection of one of the three ports or the control word registers. Input and Output data are latched. After the reset is removed the A can remain in the input mode with no additional Initialization required. 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.

They are normally connected to the least significant bits of the address bus A0 and A1. Data is transmitted or received by the buffer upon execution of input or output instructions by the CPU.

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Kasida 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. Explain with block diagram working of PPI. Computer architecture Practice Tests. 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. Used in Group A only. The 4-bit port is used for control and status of the 8-bit data port.


8255 Programmable Peripheral Interface Chip

Both Inputs and Outputs are latched. This allows a single A to service a variety of ppu devices with a simple software maintenance routine. Computer architecture Interview Questions. Hcip 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 a later time.


Intel 8255

Vudozahn 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. 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. Definition of Microprocessor 1. Intel — Wikipedia The functional configuration of each port is programmed by the systems software.

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