Universal synchronous and asynchronous receiver-transmitter: Difference between revisions

Revision as of 08:55, 16 December 2015

Revision as of 08:58, 16 December 2015

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* USARTs in synchronous mode transmits data in [[Frame (networking) |frames]]. In synchronous operation, characters must be provided on time until a frame is complete; if the controlling processor does not do so, this is an ''"underrun error''," and transmission of the frame is aborted.

* USARTs operating as synchronous devices used either character-oriented or bit-oriented mode. In character (STR and BSC) modes, the device relied on particular characters to define frame boundaries; in bit (HDLC and SDLC) modes earlier devices either relied on physical-layer signals, while later devices took over the physical-layer recognition of bit patterns.

* A synchronous line is never silent; when the modem is transmitting, data is flowing. InWhen character-orientedthe physical layer indicates that data is modeflowing, a USART will send a steady seriesstream of synchronizationpadding, either characters; inor bit-orientedbits modeas thisappropriate padding is provided byto the physicaldevice layer.or protocol

== Devices ==