GE Industrial Solutions WattStation Pedestal EVSE Charger MODBUS Register Mapping Guide - Manual (Page 7)

WattStation TM EV Charger MODBUS Register Guide
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3 EVSE MODBUS Communication Architecture
3.1 MODBUS/TCP Communication Topologies
EVSE adopts MODBUS/TCP communication acting as a MODBUS/TCP server for integrating with the
building management system. In this architecture, a MODBUS Gateway may be needed to connect
BMS from its field bus network to the Ethernet network as shown in Figure 3.1.
The MODBUS Gateway:
• is implemented as a MODBUS/TCP Client
• identifies the EVSE (MODBUS/TCP server) using EVSE IP address
• maintains the Unit ID of EVSE
• is responsible for corresponding the Unit ID to the EVSE IP address.
Inside the BMS, each EVSE may have a unique unite ID to distinguish each other. The MODBUS Client
devices in the BMS recognize each EVSE with its unit ID for MODBUS communication.
The architecture and design of the MODBUS Gateway and MODBUS/TCP clients are out of the scope
of this specification.
EVSE and BMS MODBUS communication topology architecture
Figure – 3.1
In any deployment environments, MODBUS/TCP client devices can directly communicate with EVSE if
they have the access privileges as shown in Figure 3.2.
EVSE MODBUS/TCP communication topology
Figure – 3.2
MODBUS/TCP
Client
MODBUS/TCP
Server
MODBUS/TCP Request
MODBUS/TCP Response
MODBUS
Client in
BMS
EVSE
(MODBUS/TCP
Server)
MODBUS/TCP Request
MODBUS/TCP Response
MODBUS
Gateway
MODBUS Request
MODBUS Response
Non Ethernet Ethernet