Handshaking signals

[Uwe Klein]

Hi,
in Flash Magic Application Note 1 is a circuit (figure 1) with tristate gates to turn the signals RST and /PSEN on and off. I also want to make the signals RxD and TXD floating when the COM port is closed, because my application needs the serial port for a another transceiver (after programming). With two additional gates this would be possible, but can I use DTR and/or RTS for switching ? I think this depends on the state of the handshaking signals in the moment when 'U' is transmitted from Flash Magic ?
Thanks

[Andy Ayre]

DTR and RTS are used to place the device into ISP before the 'U' is transmitted. So, yes you could use these signals to tell when the device is being reset - if that helps. You can also configure Flash Magic to keep RTS asserted during the whole time ISP is being used. See section 7.3.1 of the manual for details.