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Nigel,You could use any stable clock you like, the rest of the circuit is the more complicated part - what EXACTLY are you trying to do?.
Nigel,
I am working on a project that uses the serial tty control pins to cause interrupts. My problem is that there are only 4 input pins to use, DCD, DSR, CTS and RNG. I was thinking that I could use the output line to trigger an interrupt? I found a chip that I can use to read that doesn't require an external clock signal but not the write side.
Nigel,
I am working on a project that uses the serial tty control pins to cause interrupts. My problem is that there are only 4 input pins to use, DCD, DSR, CTS and RNG. I was thinking that I could use the output line to trigger an interrupt? I found a chip that I can use to read that doesn't require an external clock signal but not the write side.
Lefty, he's using the control lines as digital I/O into the computer to avoid using a clock. I've seen people use it like that before. If you want and you can pole the serial port fast enough you can actually use those condition lines to transmit clocked serial data. Just pick one line as a clock and sample the UART faster than 4 times the incoming clock rate. That gives you three bits to use for data. Not ideal but it works.