YASKAWA iQpump Series Programming Manual page 84

Message Format
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In Modbus communication, the master sends commands to the slave, and the slave responds. The message format is configured for both
sending and receiving as shown below. The length of the data packets is changed by the command (function) contents.
The space between messages must support the following:
Figure 1.79
Slave Address
Set the iQpump drive address from 0 to 32. If 0 is selected, commands from the master will be broadcast (i.e., the iQpump drive will not
return responses).
Function Code
The function code specifies commands. There are four function codes supported by the Drive, as shown below.
Function Code
(Hexadecimal)
03H Reading/Holding Register Contents
06H Write In Single Holding Register
08H Loopback Test
10H Write In Several Holding Registers
* Minimum bytes for a normal Response Message (error response message is always 5 bytes).
Data
Configure consecutive data by combining the storage register address (test code for a loopback address) and the data the register contains.
The data length changes depending on the command details.
Error Check
Errors are detected during communication using CRC-16. Perform calculations using the following method:
1. The factory setting for CRC-16 communication is typically zero, but when using the Modbus system, set the factory setting to one
(e.g., set all 16 bits to 1).
2. Calculate CRC-16 using MSB as slave address LSB, and LSB as the MSB of the final data.
3. Calculate CRC-16 for response messages from the slaves and compare them to the CRC-16 in the response messages.
84
Figure 79 Message Format
DDC to Drive
Drive to DDC
Command message Response message
H5-06
24 bits long
setting
Figure 80 Message Spacing
Table 21 Modbus Function Codes
Function
Slave address
Function code
Data
Error check
DDC to Drive
Command message
5 ms min.
24 bits long
Command Message
Min. (Bytes) Max. (Bytes)
8
8
8
11
Time (Seconds)
Response Message
Min.* (Bytes)
8 7
8 8
8 8
41 8
YASKAWA TM.iQp.02 iQpump Drive Programming Manual
Max. (Bytes)
37
8
8
8