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ch11-82C55PPI

ch11-82C55PPI - Programmable Peripheral Interface 82C55 EE...

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Programmable Peripheral Interface — 82C55 EE 3750 2 3 ports, 2 groups 82C55 is a parallel interface Contains 3 8-bit ports port A port B port C These are treated as 2 groups group A (port A and upper half of port C) group B (port B and lower half of port C) Why split port C? In some modes, part of port C carries control signals, rather than serving as an I/O port.
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3 Operational modes Mode 0 - basic input/output Mode 1 - strobed input/output Mode 2 - bidirectional input/output figure from Brey 4 Programming the 82C55 Command register 1 1 Port C 0 1 Port B 1 0 Port A 0 0 Function A_0 A_1 Port addresses Command register contents: A - setting ports A, B, C; B - set/reset bits of port C
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figure from Brey 5 Example initialization Command register 1 1 Port C 0 1 Port B 1 0 Port A 0 0 Function A_0 A_1 Write an 8086 instruction sequence to initialize an 82C55 programmable peripheral interface. Set Group A to operate in Mode 0 with Port A as an input port and the upper part of Port C (PC7- PC4) as an output port.
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