Getty Respawing on ISC 2.2

[Kenneth Ray Harris]

I am trying to get a dialup line running on an ISC V2.2 system.
I have two serial ports on the system configured as standard 
COM1 and COM2 ports. I try running a getty on /dev/ttyd0 and it
displays an error about respawing too fast. The manual suggests
that this means that the port has not been configed properly in
the kernel or that there are interrupt conflicts occuring with
another device. As far as I can tell, this is not the case. I
have a serial mouse connected to /dev/tty01 for use with X and
it works fine. VPIX is able to access /dev/tty00 and it works fine.
What am I doing wrong? Any suggetsions would be greatly appreciated.