Data Format; Command Frame - Omron E5AN Communications Manual

SECTION 5 Modbus Communications Procedure

5.1 Data Format

■ Command Frame

Slave address
Function code
Data
CRC-16
5-2
The data format complies with the Modbus (RTU) communications
protocol, so commands from the host and responses from the E5CN/
AN/EN/GN 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 alpha-
betic characters without the H' prefix are ASCII characters.
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 1
CRC-16 calculation range
Silent interval of 3.5 character times minimum.
Specify the unit number.
The unit number can be set between H'00 to H'63 hexadeci-
mal (0 to 99 decimal).
Specify H'00 for a broadcast transmission. No responses will
be returned for broadcast transmissions.
The function code is a 1-byte hexadecimal code that indicates
the type of command sent from the host device.
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.)
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.
CRC-16
Data
2 bytes