Comm port programming

[AmkG]

Hello all, my mind's been getting rusty lately, I need information on programming the comm ports directly (hardware level) and hopefully also be able to do autodetection of any modems and comm ports (including IRQ's).

Now what I remember is that the I/O ports are located at pretty standard places, and that in general I want to be able to respond quickly to received characters (which means using IRQ's). Each port has four registers I think, but they take up 8 addresses because they're repeated (I think). They used to have pretty standard IRQ's but no longer.

Now my idea of autodetection of IRQ's is to first determine the I/O addresses (which are pretty standard) and setup a loopback function, then trap each candidate IRQ and send a byte, which should be received immediately and call the IRQ. Is this process correct? How stable is this operation? How reliable is it?

Detection of modems I think should be easy, just send "AT\0xd\0xa" and check if you received an "OK".

"Information has a tendency to be free. Which means someone will always tell you something you don't want to know."

 

[AmkG]

Also need info on the HAYES command set, the most important of which is HOW THE HECK DO YOU TELL THE MODEM TO HANG THE PHONE!! I keep sending ATH but it just gets sent to the remote computer. I try +++<enter> ATH<enter> but it doesn't seem to always get hung up. Maybe I should do +++ATH ???

Also... just how important are those RTS CTS DCD lines? Doesn't HAYES cover all of those? Isn't DCD = CONNECT xxx? /DCD = NO CARRIER?? Do I really need to use those freaking lines? &quot;Information has a tendency to be free. Which means someone will always tell you something you don't want to know.&quot;