[comp.os.msdos.programmer] Anyone have experience using a Uart in loopback mode.

barbourj@mozart.cs.colostate.edu (jim barbour) (04/24/91)

I have need to simulate a loopback plug connected to my serial port.  Its
for writing and testing some transport protocols.

I've figured out how to put my serial port in LoopBack mode, but it will not
respond once I've done so.

Can anyone help?

Thanks,

Jim barbour (barbourj@cs.colostate.edu)

dj@ctron.com (DJ Delorie) (04/24/91)

In article <14466@ccncsu.ColoState.EDU>, barbourj@mozart.cs.colostate.edu (jim barbour) writes:
> 
> I have need to simulate a loopback plug connected to my serial port.  Its
> for writing and testing some transport protocols.
> 
> I've figured out how to put my serial port in LoopBack mode, but it will not
> respond once I've done so.
> 

Watch out for this bug - when in loopback mode, you will NOT get the
(transmit or receive, I don't remember) interrupt anymore.  You will
get the other one.  It's far easier and better to get a connector and
connect pins 2 & 3 together, and have a real loopback connector.  If
this isn't feasible, you'll have to adjust the software to compensate
for this bug.

DJ
dj@ctron.com