Default Port Modes

All ports on all ACC cards are in Loopback (Tri-state) mode when the system in which the cards are installed is powered down.

All ports on all cards are in Loopback mode when the system is powered up, but the zmon utility has not yet been run in order to bring up the ZCOM subsystem.

The ports may be in Loopback, RS-232, X.21, etc. mode when the system is brought up and zmon is scheduled (by zmasterd) to bring up the ZCOM subsystem, depending on the TTGEN configuration file that corresponds to the .tmem file used to bring up the subsystem. That is, those ports that are configured to be in Loopback mode will be in Loopback mode. Those that are defined to be in RS-232 mode will be in RS-232 mode, etc.

Those that are not defined will also be in Loopback mode. (This would be the case for ports that are on a MUX that is installed into the system but is not included in the TTGEN configuration file.)