8051_Interfacing Using RS232

This project shows 8051 interfacing using RS232. To simulate circuit in this project, initially activate Mixed Mode simulator from the Schematic Editor window. Simulation can be performed by selecting Run Transient analysis (Oscillograph) or Analysis -> Transient Analysis from Simulation menu.

The circuit has two modules, the transmitter and the receiver. Both the transmitter and receiver contains 8051 chips and MAX 232. The 8051 microcontroller sends and receives data through RS232 interface. RS232 uses MAX232 as a level converter, since standard serial interfacing of microcontroller (TTL) with RS232C Standard device, requires TTL to RS232 Level converter.

In this circuit, Port P2 (P2.0 - P2.7) of 8051 chip in the transmitter is set as the input port. The TxD pin of 8051 transmits the serial data to the receiver's RxD pin using RS232 interface and the data is output through port P2 (P2.0 -P2.7) of 8051 in the receiver ,which is set as the output port.

The source code is written Assembly language and can be viewed from the code editor window.

The program is as shown below:

Transmitter Module:

MOV TMOD,#0x20 ;TIMER1,MODE 2,AUTO RELOAD

MOV TH1,#-6 ;4800 BAUD RATE

MOV SCON,#0x50 ;8-BIT,1 STOP,REN ENABLED

SETB TR1 ;START TIMER 1

AGAIN:

MOV SBUF,P2 ;P2 TO BE TRANSFERRED

HERE:

JNB TI,HERE ;WAIT FOR THE LAST BIT

Receiver Module

MOV TMOD,#0x20 ;TIMER1,MODE2

MOV TH1,#-6 ;4800 BAUD

MOV SCON,#0x50 ;8-BIT,1 STOP,REN ENABLED

SETB TR1 ;START TIMER1

HERE:

JNB RI,HERE ;WAIT FOR CHAR TO COME

MOV A,SBUF ;SAVE INCOMING BYTE IN A

MOV P2,A ;SEND TO PORT1

The source code in the code editor window has to be compiled after making any modifications

(editing). Also the code can be debugged during simulation.