everything about communication

2. transfer of data between two entities.
Classification:
-Parallel
-serial

3. Serial versus parallel data transfer

5. Two basic transmission modes:
-Asynchronous: transmitter and receiver
clocks are independent.
-Synchronous: transmitter and receiver
modes are synchronized.

6.  Framing:
-Data word(octet) is encapsulated between
start bit
stop bit c
-receiver resynchronizes again at a start of each new word
or character received.

8.  Its an industry acronym which stands for
Universal Asynchronous Receiver
Transmitter.
 It is the interface circuitry between the
microprocessor and the serial port.
 It is responsible for breaking apart bytes of
data.
And transmitting it one bit at a time(i.e.
Serially)

9. It was designed by EIA(Electronics
Industries Association).
Voltage specifications:
-3V to -25V -- logic 1
+3V to +25V -- logic 2
Some specific signals

11. SBUF: Serial Buffer Register
-data moved to SBUF is transmitted
serially.
-serial data Rx-ed is stored by 8051 in
SBUF.
Example:
SBUF=‘char’;
variable=SBUF;
SFR: special function register

16.  This only applies to Serial Port modes 1 and 3.
 The Baud Rate is determined based on the
oscillators frequency when in mode 0 and 2.
 In mode 0, the baud rate is always the oscillator
frequency divided by 12.
 This means if your crystal is 11.059Mhz, mode 0
baud rate will always be 921,583 baud.
 In mode 2 the baud rate is always the oscillator
frequency divided by 64, so a 11.059Mhz crystal
speed will yield a baud rate of 172,797.

17. PC Baud rates
110
150
300
600
1200
2400
4800
9600
19200

18.  The basic equation for a timer reload value
can be stated as:
TH1 = 256 – Crystal Frequency/384 (or 192 if SMOD = 1)
Baud Rate
Example:
To obtain a timer reload value for a 9600 baud
serial data rate with an 11.0592 MHz crystal:
=256 – 11.0592/384
9600
= 256 – 3
= 253 or FD (hexadecimal)

19. The equation can also be solved to derive
the baud rate or the crystal frequency from
the other information as follows:
Baud Rate = Crystal Frequency/384 (or 192 if SMOD = 1)
256 – TH1