Download E5CN-H E5AN-H E5EN-H Digital Controller - Innovative-IDM

SECTION 5 Modbus Communications Procedure
5.1 Data Format
The data format complies with the Modbus (RTU) communications
protocol, so commands from the host and responses from the E5CN/
AN/EN-H are contained in data blocks called frames.
The structure of the command and response frames is described below.
In the following explanations, hexadecimal values are expressed by
adding the prefix H’ before the number, e.g., H’02. Numbers and alphabetic characters without the H’ prefix are ASCII characters.
■ Command Frame
When using RTU mode, start with a silent interval of at least 3.5
character times and end with a silent interval of at least 3.5 character
times.
Slave Function
address code
1
Data
CRC-16
1
2 bytes
CRC-16 calculation range
Modbus
Silent interval of 3.5 character times minimum.
Slave address
Specify the unit number.
The unit number can be set between H’00 to H’63 hexadecimal (0 to 99 decimal).
Specify H’00 for a broadcast transmission. No responses will
be returned for broadcast transmissions.
Function code
The function code is a 1-byte hexadecimal code that indicates
the type of command sent from the host device.
Data
This is the text data associated with the specified function
code. Specify the required data, such as the variable address
or setting data. (Set in hexadecimal.)
CRC-16
Cyclical Redundancy Check
This check code is calculated with the data from the slave
address to the end of the data.
The check code is 2-byte hexadecimal.
Silent interval of 3.5 character times minimum.
5-2