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?.
This is a little confusing. The control signals (DCD,DSR,etc) are single independent digital input or output signal lines that have no timing relationship with any possible clocked serial data on the send and receive lines. These are not serial signals but rather parallel logic signals. You don't need clock timing to send or receive these control lines, just possibly voltage level converters depending on what voltage levels are being used on the two sides of the control signal(s).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.
Hardly an 'exact' description of what you're trying to do, it doesn't even mention what you're using, or what you're trying to do - it really still tells us nothing.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.
Yes, I know about bit banging asynchronous serial data, but it's not clear at all that is what he is trying to do but I wish him luck anywayLefty, 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.