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8255 Programmable Peripheral Interface: Pin Details & Modes

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  1. 8255 Programmable Peripheral Interface

  2. Pin details

  3. The internal block diagram of 8255

  4. Port Address

  5. Data bus D[7:0] PA[7:0] A0 8086 PB[7:0] A1 RD Control port WR PC[7:0] RESET A7 CS A6 A5 A4 Port A3 A1 A0 A2 • 0 0 • 0 1 • 0 • 1 1 PA PB PC Control IO/M I/O port address

  6. Different modes Mode 0: Simple Input or Output • Ports A, B, and C can be individually programmed as input or output ports • Port C is divided into two 4-bit ports which are independent from each other Mode 1: Input /Output Control Signals • Ports A and B are programmed as input or output ports • Port C is used for handshaking Mode 2: Bidirectional Data transfer • Port A is programmed to be bi-directional • Port C is for handshaking • Port B can be either input or output in mode 0 or mode 1

  7. Bit set reset Mode

  8. Control word format for I/O mode

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