ProSoft Technology MVI56-AFC - Manual (Page 129)

MVI56-AFC ♦ ControlLogix Platform Events
Liquid and Gas Flow Computer User Manual
ProSoft Technology, Inc. Page 129 of 316
February 25, 2011
9.5.3 Virtual Slave Precedence Relations
Addressing conflicts (collisions) can arise among three distinct regions of the
Virtual Slave holding register bank. These regions are:

The defined range of 9900 registers to which Primary Slave registers may be
mapped.

The word region of the pass-thru configuration, significant for Modbus write
commands only.

The LDW, specified in this document, when mapped to the Virtual Slave via
Ph00147.
An addressing collision arises when the address of a holding register falls within
more than one region. The AFC resolves such collisions as follows:
Each address is deemed to fall into one of (i) the pass-thru word region, (ii) the
LDW, or (iii) the 9900-register defined range, whichever occurs first.
All Virtual Slave registers addressed by a single Modbus transaction must reside
in the same region; no region-spanning is permitted. A region-spanning
transaction is rejected with Modbus exception code 2, Illegal Address.