Fuji Electric ZKM, Руководство по обслуживанию

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INZ-TN5A0506-E
5.2 Composition of Message
Command message and response message consist of 4 fields; Station No., Function code, Data and Error check
code. And these are sent in this order.
Station No. (1 Byte)
Function Code (1 Byte)
Data Part (2 to 133 Bytes)
Error check code (CRC-16) (2 Bytes)
Fig. 5-1 Composition of message
In the following, each field is explained.
(1) Station No.
Station No. is the number specifying a slave station. Only a slave station that corresponds to a value to
which “Station No.” is set on the analyzer maintenance mode display executes a command.
(2) Function code
This is a code to designate the function executed at a slave station.
For details, refer to section 5.4.
(3) Data part
Data are the data required for executing function codes. The composition of the data part is different
depending on the function code. For details, refer to chapter 6.
A register number is assigned to each data in the analyzer. For reading/writing the data by communication,
designate the register number.
Relative address =






Coil number or register number
of last 4 digits.
– 1
For example, the register number specified by certain function code = in case of 4003
Relative address = (Lower 4 digits of 40003) – 1
= 0002
The message above will be used.
(4) Error check code
This is the code to detect message errors (change in bit) in the signal transmission.
MODBUS protocol (RTU mode) uses CRC16 (Cyclic Redundancy Check).
For CRC calculation method, refer to section 5.5.