Introduction to Interfacing Technique

[object Object],[object Object],[object Object],[object Object],[object Object],CHAPTER 1 Introduction to Interfacing Techniques & Data Transfer Schemes

Interfacing ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

μP ,[object Object],[object Object],[object Object],[object Object]

Definitions: ,[object Object],[object Object],[object Object],[object Object]

Interface Definitions ,[object Object],[object Object],[object Object],[object Object]

Cont… ,[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object]

Components of Interface The interfacing devices should make use of standard data transfer schemes for the efficient exchange of data. Interface Signals Interface Signals Interfacing Device (ID 1) Interfacing Device (ID 2) Interfacing Standards & Converters

Data Transfer Schemes ,[object Object],[object Object],[object Object],[object Object],For effective data transfer between these devices, the timing parameters of the devices should be matched. But most of the devices have incompatible timings.

Two Categories: ,[object Object],[object Object]

Programmed Data Transfer ,[object Object],[object Object],[object Object],Examples of devices using parallel data transfer are ADC,DAC, Hex-keyboard, 7-segment LED's, etc.

3 Types of Programmed Data Transfer ,[object Object],[object Object],[object Object],[object Object]

Direct Memory Access (DMA) Data Transfer ,[object Object],[object Object],[object Object],Typical examples of devices using DMA are CRT controller, floppy disk, hard disk, high speed line printer, etc

3 Types of DMA Data Transfer ,[object Object],[object Object],[object Object],[object Object]

Types of Data Transfer Schemes

PROGRAM CONTROLLED TRANSFER ,[object Object],[object Object],an i/o operation takes place only when an i/o instruction is encountered in the execution of the program synchronous transfers mean transfers occurring at the same time asynchronous transfers mean transfers taking place at irregular intervals Data transfers between the microprocessor and the peripherals are primarily asynchronous

Program controlled data transfers can take place under several conditions ,[object Object],[object Object],[object Object],[object Object],[object Object],assumes that a peripheral is always available kept in a loop to check whether data are available interrupted from its normal execution of program by an I/O device, when the latter is ready when peripheral response time is slower than the microprocessor execution time, READY signal is used handshake signals are signals exchanged prior to data transfer

Synchronous data transfer scheme ,[object Object],[object Object],[object Object],the mode-O input or output in 8155 or 8255 is an example of synchronous data transfer

Asynchronous Data Transfer Schemes ,[object Object],[object Object],[object Object],[object Object],[object Object],handshake data transfer without interrupt (mode-l and mode-2) of8155 or 8255 is an example

Interrupt Driven Data Transfer Scheme ,[object Object],the processor first initiates the I/O device for data transfer. After initiating the device, the processor will continue the execution of instructions in the program. Also at the end of an instruction the processor will check for a valid interrupt signal. If there is no interrupt then the processor will continue the execution. When the IO device is ready, it will interrupt the processor. On receiving an interrupt signal, the processor will complete the current instruction execution and saves the processor status in stack. Then the processor call an interrupt service routine (ISR) to service the interrupted device.

PROGRAM CONTROLLED DMA TRANSFERS ,[object Object],In programmed data transfer, a memory resident routine requests the device for data transfer to and from one of the microprocessor registers Programmed data are used when relatively small amounts of data are transferred using relatively slow I/O devices such AID, D/A converters, and peripheral floating point arithmetic unit. DMA is preferred when a large block of data is to be transferred. This scheme is generally employed for transferring data between the microprocessor and peripheral mass storage devices like hard disk or a high-speed line printer.

INTERRUPT PROCESS IN MICROCOMPUTERS ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Introduction to Interfacing Technique

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