SEW-Eurodrive ECDriveS ECIO-8-24-00, Manual

Page: 29 / 43

Startup
6
Manual
– ECDriveS® 29
So, no matter which of the three connection protocols you use (Modbus TCP, EIP, or
Profinet I/O), for any given assembly, the internal data you are accessing with your P LC
is the same
Modbus assembly instance structure
Each ECIO utilizes Modbus register architecture for remote data access over E t hernet .
Modbus TCP is a simple protocol for data exchange based upon a query/response
mechanism. Each module’s memory structure contains a fixed array of internal data loca-
tions that are constructed as Modbus Holding Registers. Each module has a fix ed re-
serve of Holding Registers with each capable of holding a 16-bit numerical integer value.
Modbus TCP protocol provides for read/write access to any available Holding Regis t er.
The structure of these registers allows for individual module’s to read from and write to
specific register address locations to achieve inter-module communications. Certain reg-
isters are read from and written to by the ECShell software in order to monitor and/or
change default configuration values.
Modbus TCP addressing convention utilizes a “4:xxxx” notation. The “4:” in Modbus pro-
tocol designates that the address is a Holding Register and the xxxx is a numerical value
representing the offset or index for a specific location. The “xxxx” values used in this
document are to be interpreted as if they are for a Modbus PLC which means that the first
register address is “4:0001” and that there is no “4:0000” register. Some PLC data struc-
tures and PC development environments utilize the “4:0000” designation and their index -
es will be offset by 1. Please refer to your PLC or PC application documentation for t he
Modbus convention used on their platforms.
Any Modbus TCP capable PC or PLC can connect to any ECIO module visible on its
network and access Input and Output Holding Register Assemblies. ECIO supports t he
following Modbus TCP Service Codes:
Service Code 3 - Read Holding Register (up to 45 registers per instruction)
Service Code 6 - Write Single Register
Service Code 16 - Write Multiple Registers (up to 45 registers per instruction)