1. transfer of data between two
entities.Classification:-Parallel-serial
2. Serial versus parallel data transfer 3. Two basic
transmission modes:-Asynchronous: transmitter and receiverclocks
are independent.-Synchronous: transmitter and receivermodes are
synchronized. 4. Framing:-Data word(octet) is encapsulated
betweenstart bitstop bit c-receiver resynchronizes again at a start
of each new wordor character received. 5. Its an industry acronym
which stands forUniversal Asynchronous ReceiverTransmitter. It is
the interface circuitry between themicroprocessor and the serial
port. It is responsible for breaking apart bytes ofdata.And
transmitting it one bit at a time(i.e.Serially) 6. It was designed
by EIA(ElectronicsIndustries Association).Voltage
specifications:-3V to -25V -- logic 1+3V to +25V -- logic 2Some
specific signals 7. SBUF: Serial Buffer Register-data moved to SBUF
is transmittedserially.-serial data Rx-ed is stored by 8051
inSBUF.Example:SBUF=char;variable=SBUF;SFR: special function
register 8. This only applies to Serial Port modes 1 and 3. The
Baud Rate is determined based on theoscillators frequency when in
mode 0 and 2. In mode 0, the baud rate is always the
oscillatorfrequency divided by 12. This means if your crystal is
11.059Mhz, mode 0baud rate will always be 921,583 baud. In mode 2
the baud rate is always the oscillatorfrequency divided by 64, so a
11.059Mhz crystalspeed will yield a baud rate of 172,797. 9. PC
Baud rates110150300600120024004800960019200 10. The basic equation
for a timer reload valuecan be stated as:TH1 = 256 Crystal
Frequency/384 (or 192 if SMOD = 1)Baud RateExample:To obtain a
timer reload value for a 9600 baudserial data rate with an 11.0592
MHz crystal:=256 11.0592/3849600= 256 3= 253 or FD (hexadecimal)
11. The equation can also be solved to derivethe baud rate or the
crystal frequency fromthe other information as follows:Baud Rate =
Crystal Frequency/384 (or 192 if SMOD = 1)256 TH1
