Rockwell Automation Publication 1715-UM001J-EN-P - December 2020
15
Chapter 1 Redundancy System Overview
1715-AENTR Adapters
The leftmost adapter position, or slot, is 0. The rightmost adapter slot is 1. One
redundant adapter pair always occupies slots 0 and 1 of the system. ‘A’
designates the primary adapter partner and ‘B’ designates the secondary
adapter partner of the redundant adapter pair. This system is designed to run
with two adapters. It can run with one adapter for a limited time while
replacing a damaged module, but ideally, needs both adapters running
simultaneously.
I/O Modules
I/O module slots are numbered from 2…25, based on distance from the adapter
base unit. If duplex I/O module pairs are used, the two modules of the pair
must be in adjacent slots. The left, lower slot number is considered the slot
number and address for the pair. Any combination of simplex modules and
duplex pairs can be used in one or more connected I/O base units.
Module Positioning in the 1715 Redundant I/O System
There are 26 total slot positions in the system numbered from 0…25. The first
two positions always contain the redundant adapter pair, in slots 0 and 1. The
remaining positions begin numbering at slot 2 and contain the I/O modules,
ending at slot position number 25. Any combination of simplex or duplex I/O
module pairs can be used in the I/O base units. See
for a sample of what
a system could look like.
Expansion cables can be used to connect base units, as shown in
.
IMPORTANT
There is no method for configuring a system to use only one 1715-
AENTR adapter. If you use only one 1715-AENTR adapter, the
unused module generates errors.
A ‘partner’ adapter can be installed or removed for replacement,
while the 1715 Redundant I/O System is operational. The ‘partner’
adapter can be identified by the Network Status Light Emitting
Diode (LED) flashing green. During replacement of the module,
there is a one-time, up to a maximum 500 ms, delay to the
system.
IMPORTANT
A ‘partner’ I/O module can be installed or removed while the 1715
Redundant I/O System is operational, without impact to the rest
of the system.
The sample system configuration in Example 1 does not match the system
layout that is displayed in Example 2. Example 1 and Example 2 are different
examples of possible configurations you can have for your system.