INTEL 8251A INTEL 8251A USARTUSART

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IINTERNAL STRUCTURENTERNAL STRUCTURE

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IInternal structurenternal structure

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IINTERNAL STRUCTURENTERNAL STRUCTURE C/D=1(CONTROL/STATUS)C/D=1(CONTROL/STATUS) =0(DATA)=0(DATA)

C/DC/D RDRD WRWR

00 00 11 DATA BUSDATA BUS

00 11 00 DATA BUSDATA BUS

11 00 11 STATUSSTATUS

11 11 00 CONTROLCONTROL

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INITIALIZATIONINITIALIZATION

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INITIALIZATIONINITIALIZATION MODEMODE WORD WORD

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MODEMODE

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COMMAND COMMAND WORDWORD::

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COMMAND WORDCOMMAND WORD

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COMMAND WORDCOMMAND WORD

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STATUS WORDSTATUS WORD

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INITIALIZATIONINITIALIZATION

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PROGRAMPROGRAM

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RS-232C standardRS-232C standard