I used 555 to control DE and RE of max485.I have found it in this:http://www.bb-elec.com/bb-elec/literature/485ptbr-3903ds.pdfWhat are the 555 circuits doing in all this
Yes.I think it is good but now i want to simulate half duplex first.I also suggest that you replace the half duplex RS485 chip (MAX487) with full duplex version (MAX488).
Yes.I used it.I made 2 breadboardThen just use this concept RS232->MAX232->MAX488------MAX488->MAX232->RS232