Thermo Scientific Micro-Tech 9101, Reference Manual

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C-64 Micro-Tech 9101/9201 Reference Manual, Rev J Thermo Fisher Scientific
This is a Modbus variant used for communications over TCP/IP networks,
connecting over port 502. It does not require a checksum calculation as
lower layers already provide checksum protection. Each device intended to
communicate using Modbus is given a unique address. In serial and MB+
networks only, the node assigned as the Master may initiate a command,
but on Ethernet, any device can send out a Modbus command, although
usually only one master device does so. A Modbus command contains the
Modbus address of the device it is intended for. Only the intended device
will act on the command, even though other devices might receive it (an
exception is specific broadcastable commands sent to node 0 which are
acted on but not acknowledged). All Modbus commands contain checking
information, ensuring that a command arrives undamaged. The basic
Modbus commands can instruct an RTU to change a value in one of its
registers, control or read an I/O port, as well as commanding the device to
send back one or more values contained in its registers.
Figure C–3. Modbus Screen
The Register Mapping of Modbus TCP/IP is the same as that of Modbus
RTU. See page C-32.
Modbus
TCP/IP
Register Mapping