User`s guide

Page 96

Controlinc 1746-C (Version 5.21) Network Master Users Guide (2004-11-18)

6.2.4. Preferred Communication Port Operation

The 1746-C operates on both communication ports. In a standard E>Net Ring topology, the

• Port 1 (top port) on the 1746-C goes to Port A on the EIM NIU.

• Port 2 (bottom port) on the 1746-C goes to Port B on the EIM NIU.

The implementation of this communication scheme works in conjunction with the aspect of

“

Communication Failure Indications” such that if a failure is detected on a particular port for a particular

actuator, it will remain “actively announced” to assist in the diagnostics and troubleshooting required by

a service technician.

The 1746-C tries to utilize both communication ports evenly. It has a “

preferred port” and a

“

backup port” such that the program will try to communicate over the preferred port to a particular

actuator. However, if there is a problem communicating with the preferred port, the program will

automatically try the backup port.

The 1746-C alternates port 1 & 2 as being the preferred port after every scan period. That is, at the

start of every diagnostic scan, the preferred port is changed. Example scenario:

1. Scan period n:

• Preferred Port: Port 1

• Backup Port: Port 2

2. Scan period n+1:

• Preferred Port: Port 2

• Backup Port: Port 1

3. Scan period n+2:

• Preferred Port: Port 1

• Backup Port: Port 2

4. ………..

If a problem is detected on the preferred port for an actuator, it will remain using the backup port until

the next diagnostic scan is made to retest the port.

During restart, after the initial diagnostic scan completes, Port 2 is initially the preferred port.