Lemme clarify- whether or not you're galvanically isolating, any RS485 transceiver needs either 3-wire or 4-wire logic due to its half-duplex nature, OR to be protocol-aware.
I don't know if the RTS could be used that way. RTS is hardware flow control, which is obsolete now and often not implemented. RTS precedes a byte, and is supposed to be a query to the transceiver which MAY be responded with a CTS (Clear to Send), at which point the START bit and the byte begin. It's mostly nonsense now, most transceivers don't work that way. Hardware flow control can be defeated just by tying the CTS line to RTS, so "I WANT to transmit" is always "ok to transmit". Hmm, if we did this, you'd lead with the Master transmit packet: Slave Address/Function Code/Byte Count/etc which would begin with RTS. It would probably leave RTS high the whole time- but I don't know if that's guaranteed. Then when the packet is done and it needs a response, RTS should be deasserted. Well it should deassert it. If it intends to play Modbus, it won't send anything else while waiting for the response. The RTS does NOT require isolation. It's on the ground-referenced side of a galv isolation transceiver. Danny On 4/4/2016 2:04 AM, Nicklas Karlsson wrote: > I think the RTS signal is common but it must of course also be insulated. > http://www.moxa.com/resource_file/857220091121341.pdf > > Nicklas Karlsson <[email protected]> > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
