8255 - UNIT-5 I / O structure of a typical microcomputer...

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8255 1 UNIT-5 I / O structure of a typical microcomputer 8255 PPI (Programmable peripheral interface) Pin diagram of 8255 Block Diagram of 8255 Architectural and programming details of 8255 Traffic light controller interfacing to 8086 through 8255 Stepper motor interfacing to 8086 through 8255 Interfacing keypad to 8086 through 8255 Interfacing DAC to 8086 through 8255 Interfacing ADC to 8086 through 8255 Interfacing 7-segment display through 8255
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8255 2 I/O structure of a typical microcomputer Input Devices Keyboard Optical input devices Card Reader Paper Tape Reader Bar code reader Digitizer Optical Mark Reader Magnetic Input Devices Magnetic Stripe Reader Screen Input Devices Touch Screen Light Pen Mouse Analog Input Devices
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8255 3 I/O structure of a typical microcomputer Output Devices Card Puncher, Paper Tape Puncher CRT Printer (Impact, Ink Jet, Laser, Dot Matrix) Plotter Analog Voice
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8255 4 I/O structure of a typical microcomputer The typical I/O structure of a micro controller is as follows Maskable Non-Maskable External I/O Structure Programmed I/O Interrupt Driven I/O DMA Data Transfer Block Transfer DMA Cycle Stealing DMA Demand Transfer DMA Standard I/O (or) Isolated I/O (or) Port I/O Memory Mapped I/O Internal Software Interrupts Due to Exceptional Conditions
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8255 5 I/O structure of a typical microcomputer Data Transfer Serial Data Transfer Parallel Data Transfer Double Hand-shaking I/O Single Hand-shaking I/O Simple I/O Simple Strobbed I/O (or) Interrupt Driven I/O Hand-shaking I/O
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8255 6 I/O structure of a typical microcomputer I/O devices serve two main purposes To communicate with outside world To store data I/O controller acts as an interface between the systems bus and I/O device Relieves the processor of low-level details Takes care of electrical interface I/O controllers have three types of registers Data Command Status
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8255 7 I/O structure of a typical microcomputer
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8255 8 I/O structure of a typical microcomputer To communicate with an I/O device, we need Access to various registers (data, status,…) This access depends on I/O mapping Two basic ways Memory-mapped I/O Isolated I/O A protocol to communicate (to send data, …) Three types Programmed I/O Direct memory access (DMA) Interrupt-driven I/O
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8255 9 8255 – PPI D7 to D0 Bi-directional Data Bus RESET RESET INPUT CS CHIP SELECT RD READ INPUT WR WRITE INPUT A0 & A1 PORT ADDRESS PA 7 to PA 0 PORT A (BIT) PB 7 to PB 0 PORT B (BIT) PC 7 to PC 0 PORT C (BIT) Vcc 5 VOLTS GND 0 VOLTS
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8255 10 8255 – PPI– Block Diagram
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8255 11 8255 – PPI The 8255/8255A is a programmable peripheral interface (PPI) device designed for use in Intel microcomputer systems. Its function is that of a general purposes I/O component to Interface peripheral equipment to the microcomputer system
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8255 - UNIT-5 I / O structure of a typical microcomputer...

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