Siemens 9350 User Manual
9300 Series User’s Guide
Using the Modbus/TCP Protocol
Chapter 3 - Default Meter Functionality
Page 59
You can use the Modbus RTU protocol to write values into ION external numeric,
pulse and Boolean modules, allowing you to enable, disable and reset meter
functions. You can also use Modbus to change setup register values in various ION
modules to configure the meter’s operation.
pulse and Boolean modules, allowing you to enable, disable and reset meter
functions. You can also use Modbus to change setup register values in various ION
modules to configure the meter’s operation.
All of the information required to write to ION registers through Modbus is
available in 9300 & 9330 Modicon Modbus Protocol, available on the Technical
Documentation CD, or by request from Siemens.
available in 9300 & 9330 Modicon Modbus Protocol, available on the Technical
Documentation CD, or by request from Siemens.
Using the Modbus/TCP Protocol
Modbus/TCP is the newest open Modbus protocol variant (formerly called
MBAP). It defines the packet structure and connection port (port 502) for the
industry standard TCP/IP protocol. The structure of Modbus/TCP is very similar
to the Modbus RTU packet except that it has an extra six-byte header and does not
use the cyclic redundancy check (CRC). Some of the newest ION firmware now
supports Modbus/TCP for direct communications with the meter.
MBAP). It defines the packet structure and connection port (port 502) for the
industry standard TCP/IP protocol. The structure of Modbus/TCP is very similar
to the Modbus RTU packet except that it has an extra six-byte header and does not
use the cyclic redundancy check (CRC). Some of the newest ION firmware now
supports Modbus/TCP for direct communications with the meter.
Modbus/TCP retains the Modbus RTU limit of 256 bytes to a packet. It is suggested
that higher through-put is possible if this limitation is removed. This variant is
called Enhanced Modbus/TCP but, so far, few devices have moved to support it.
that higher through-put is possible if this limitation is removed. This variant is
called Enhanced Modbus/TCP but, so far, few devices have moved to support it.
Another variant, that has yet to gain popularity, is from the Semiconductor
Equipment and Materials International (SEMI) trade association. The Generic
Sensor-Bus Sub-Committee created the Sensor/Actuator Network Standard (SEMI
E54-0997).
Equipment and Materials International (SEMI) trade association. The Generic
Sensor-Bus Sub-Committee created the Sensor/Actuator Network Standard (SEMI
E54-0997).
Modbus TCP Communications
You can now communicate to the meter via Modicon
®
Modbus TCP (formerly
called MBAP). Your meter must have the optional Ethernet port.
Connect to socket 502.
Connect to socket 502.
Be aware that you cannot form an EtherGate connection to the Modbus TCP
network.
network.
Ethernet
Connect to socket 502
Meter with optional
Ethernet port
Ethernet port