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5.4 Detailed Description of the Services
■ Read Variable Area
Command Frame
Slave
address
1
Slave address
Function code
Read start address
Number of elements
CRC-16
To read from the variable area, set the required data in the command
frame, as shown in the following diagram.
Function
Read
code
start address
H'03
1
2
Name
Specify the E5CN's unit number.
The unit number can be set between H'01 and H'63 hexadecimal (1
to 99 decimal).
The Read Variable Area function's function code is H'03.
Specify the address containing the data to be read.
See SECTION 6 Communications Data for Modbus for details on
addresses.
Specify 2 times the number of setting data items as the number of
elements to be read. The setting range for the number of elements is
H'0002 to H'0010 (2 to 16).
Example: When reading 2 items of setting data, set the number of
elements to H'0004.
This check code is calculated with the data from the slave address to
the end of the data.
For details on the CRC-16 calculation, see CRC-16 Calculation
Example in 5.1 Data Format on page 5-3.
5.4 Detailed Description of the Services
Number of
CRC-16
Elements
2
2 bytes
Description
5-9
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