Hi Ted, you missunderstood me. This special UART does all the required stuff in hardware. You only have to enable this mode once by writing some magic to a UART register. From that time on the UART will automatically assert the RTS# line when transmitting. I am not talking about a software implementation. Your arguments deal with a software implementation where you have to do it all by hand, which will not work safely as you mentioned. Matthias > On Wed, Dec 17, 2008 at 10:24:13PM +0100, Matthias Fuchs wrote: > > Hi, > > > > some Exar UARTs like the XR16C2850 support a feature > > called auto RS485 half-duplex control. In this mode the > > RTS line has a special role when using the UART for > > RS485 communication. > > So I haven't maintained the serial driver for a long time, but when I > did, I refused to try to implement hardware half-duplex control > because there was absolutely no standards in this space. Which RS-232 > lines are involved wasn't standardized, and there was often very > strange timing restrictions as well. Some devices required there to > be a minimum delay of XX milliseconds between when RTS is raised > and when DTR is raised. Other devices have a maximum time between > when one side raises RTS and the others side raises DTR. > > So the challenge is designing an interface for half-duplex which is > sufficiently general that it will actually work for all/most of the > half-dozen people in the world who still care about half-ruplex RS-232 > communications. :-) > > - Ted > -- > To unsubscribe from this list: send the line "unsubscribe linux-serial" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
