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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 send in this order.
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
Data are the data required for executing function codes. The composition of data varies with function
codes. 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.
Note that the register number transmitted on message is expressed as its relative address.
The relative address is calculated by the following expression.
Relative address ＝
For example, when the resister number designated by a function code is 40003,
Relative address
= 0002
is used on the message.
8
Station No. (1 byte)
Function code (1 byte)
Data (2 to 133 bytes)
Error check code (CRC-16) (2 bytes)
Fig. 5-1 Composition of message
The lower 4 digits of the Register number
= (lower 4 digits of 40003) – 1
– 1
INZ-TN5A1190-E
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