Serial communication based on 51 single chip microcomputer

One , Concept of computer communication ： The computer is on = Information exchange with external devices or computers .

Two ,89C51 Serial port of SCON                                                                                                                1, structure                                                                                                                                                                                                                                                                                                 SCON It's a special SCON Is a special function register , Used to set the working mode of serial port , receive / Send control and set status flags

 

2, To configure                                                                                                                                               ******SM0 and SM1：SM0 and SM1 Select bit for working mode , There are four ways to work , Usually used 1.                                                        

******SM2 Multi machine access control bit , Mainly used in 2 And way 3. When the receiver SM2=1 when , You can use what you receive RB8 To control whether to activate RI（RB8=0 Not active when RI, The received message is discarded ;RB8=1 when , The received message enters SBUF, And activate RI, In turn, the data is transferred from SBUF Go to read ）. When SM2=0 when , No matter what you receive RB8 yes 0 still 1, Can make the received data enter SBUF, And activate RI（ here RB8 Don't control RI）.                                                In ways 0 when ,SM2 Must be 0, In ways 1 when , If SM2=1, Then only when a valid stop bit is received ,RI Can be set 1.

******REN, Allows serial reception of bits . Set by software REN=1, start-up , Set up 0 To close .

******TB8, In ways 2 Or the way 3 in , Is the ninth bit of received data , Its function can be specified by software . Can be used as parity bit of data . In ways 0 And way 1 The middle bit is not used .

*******RB8, In ways 2 or 3 in , The ninth bit of the received data . In ways 1 when , if SM2=0, be RB8 Is the received stop bit .

******T1, Send interrupt flag bit . In ways 0 when , When the serial port sends the eighth bit data , Or in other The way , When the serial port sends the stop bit , By internal hardware T1 Set up 1, towards CPU Send interrupt request . In the interrupt program , The software must be clear 0, Cancel this interruption request .

******RI, Receive interrupt flag bit , In ways 0 when , When the serial port receives the eighth bit data , Or in other ways , When the serial port receives the middle of the stop bit , By internal hardware RI Set up 1, towards CPU Send interrupt request . Must be in the interrupt program , Use software to clear 0, Cancel the interruption Application .

3、 ... and ,PCON

                    SMOD（PCON.7） Baud rate multiplication . In ways 1,2,3 when , Baud rate and SMOD of , When SMOD=1 when , Double the baud rate , Reset time ,SMOD=0.