Rs-485 And Rs-232

[transfomer]

http://www.dzsc.com/data/uploadfile/2008425105430490.jpg

i found this circuit in a site ,just carrying out it ,i use RS232 before ,will rs485 the same to it ,is there a differ in program

 

TL750L05,SN75LBC184

 

[marke]

Hello transformer

 

When you use RS485, you are using the same circuit between your master and slave for TX and RX. With RS232, you have a TX line and an RX line.

 

For RS485, you need to switch the transceiver, in your circuit SN75LBC184, between transmit and receive.

This is done by controlling the direction pin and in your diagram, this is controlled by P16 on the micro.

 

You leave the transceiver in RX mode until you want to send data. Then you switch to transmit mode and wait until the data has been sent and then switch back to receive mode. The timing is critical as if you switch too soon, you will block some data from going out, and if you switch too late, you may miss some data from coming in.

 

Best regards