Chapter 7 Serial Communication -- An Introduction

Chapter 7 Serial Communications

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Parallel I/O vs Serial I/O •

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Parallel I/O: 8 or more lines are used to transfer data simultaneously. Serial I/O: 1 line is used. Data is sent one it at a time.

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!eatures of Parallel Communications 1. Parallel I/O uses many si"nal pins PO#$% & 8 its $#IS% & 8 its for data transfer direction direction 'C( has limited numer of pins. ). (sually used for very short distances* due to $imin" s+e,: $he si"nals arrive at different times. Crosstal+: Si"nal transmitted in one channel creates an undesired effect in another channel.  –

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-. Cale for parallel transfer is more e%pensive 3

Serial Communications •

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$he transfer of di"ital data over over a sin"le data transmission line one it at a time. hy  –

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#educe the cost of IC pac+a"e y reducin" the numer of pins used for communication. $imin" s+e, et,een different channels is not an issue. 0 serial connect reuires fe,er interconnectin" cales and hence occupies less space.

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$,o ma2or dra,ac+s of Parallel I/O $imin" S+e,

Crosstal+

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Duple% 'ode Simplex:

Half duplex:

Full duplex:

Synchronous vs 0synchronous 1.  Synchronous Synchronous 0 synchroni3in" cloc+ si"nal is transmitted for synchroni3ation. 2.  Asynchronous 4o cloc+ si"nal is transmitted from the transmitter transmitter to receiver. On each end* the internal cloc+ must e the same. #ely on e%tra its that are ,rapped around the yte to e sent 5start it* stop it6.  –

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PIC18 Serial 'odule •

PIC18 family microcontrollers have several uiltin modules for serial communication:  –

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(0#$/(S0#$/(S0#$ for for asynchronous communication I)C port for synchronous  communication communication ,ith other I)C peripherals.

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