You can communicate with the series 300 switches Group G controller via the RS-485 port if the ATS has the optional Accessory 11BE.
The Accessory 11BE is a four-function software bundle.  One of the four functions is to allow the user to configure the RS485 communications port.  Please see Group G Controller Users Guide .
The image below will show you the location of the RS485 port and the S7 & S8 dipswitches.
For the proper RS485 port terminal designations, please refer to the ATS wiring diagram.  For generic Series 300 Group G wiring diagrams, please click this link .
For 2-wire serial connection, set S8 dipswitch actuators over to the right (ON position), and choose to connect your two wires on either the Rx terminals or the Tx terminals.
If you're communicating via MODBUS, click this link for a copy of the MODBUS register map for the Series 300 Group G controller.
If unsure, contact Technical Support at 1-800-800-ASCO or send an email to technicalsupport@ascopower.com
You may also watch the videos related to this (please see below).
Published for:ASCO Power Technologies USA