hello Donatas

just explanning u brief..so u can get clear picture about rs-232.

flow control is used to synchronise transmitter and
receivers buffers...just avoiding receiver buffer not to miss any data..if they are full..

one way is hardware flow control..were hardware pins in 9-pin connector are used to have synchro between transmitter and receiver..( RTS,CTS,DTR etc..)


other way is softawre flow control..Xon/Xoff..

here..Xon means establish software syncro between transmitter and reciever..sending some control characters along data..

that is if..receiver buffer is full..then receiver UART
will send some control characters to transmitter to stop transmitting data for while..and again resume when
receiver buffer is empty to hold futher data

its just sending control characters between tranmitter and receiver to acheive the flow control..

Xoff - not to establish this flow control...

also other option is NO FLOW CONTROL..
so all together each flow control differ from each other..

I HOPE THIS BREIF INFORMATION WOULD HELP YOU...

regards,

santosh