Department of Computer Scien

ce and Information Engineering

National Cheng Kung University

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SERIAL COMMUNICA-TION

PROGRAMMINGDoubling Baud

Rate

‰There are two ways to increase the baud rate of data transfer

¾To use a higher frequency crystal¾To change a bit in the PCON register

‰PCON register is an 8-bit register

¾When 8051 is powered up, SMOD is zero¾We can set it to high by software and thereby double the baud rate

IDL

PD

GF0

GF1

--

--

--

SMOD

MOV A,PCON ;place a c

opy of PCON in ACC

SETB ACC.7 ;make D7=1MOV PCON,A ;changing any other bits

It is not a bit-addressable register

The system crystal is fixed