METSOmaxPAC Hardware Reference Guide

In Figure 1-5a, the terminator is shown inserted into connector P9 of the top 

rack in cabinet 2. That is the point on the bus that is farthest from the DPU. 

If you add I/O racks to your system at a later date, remember to move the 

terminator from its old location to the new end of the bus. 

I/O Bus Terminators are not used to provide impedance matching. They are 

simply pull-up resistors that are used to improve the rise time of the open 

collector I/O bus signals. For that reason, in some instances (e.g., a system 

with both maxPAC and 564-style I/O connected with long cable runs), an 

additional terminator at the DPU end might be required. Monitor the I/O Bus 

Errors and, if your system seems to have an excessive amount, try adding the 

additional terminator. 

Refer to the Bus Extender Module chapter in this manual for information on 

how to install terminators when BEMs are present in the system