C.7 Message Format
YASKAWA ELECTRIC
TOEP C710656 07A YASKAWA Power Regenerative Converter - D1000 Instruction Manual
209
MEMO
BUS/Mod
bus
Co
mmunica
tion
s
C
C.7 Message Format
◆
Message Content
In MEMOBUS/Modbus communications, the master sends commands to the slave, and the slave responds. The message
format is configured for both sending and receiving as shown below, and the length of data packets depends on the
command (function) content.
◆
Slave Address
The slave address in the message defines the note the message is sent to. Use addresses between 0 and FF (hex). If a
message with slave address 0 is sent (broadcast), the command from the master will be received by all slaves. The slaves
do not provide a response to a broadcast type message.
◆
Function Code
The three types of function codes are shown in the table below.
◆
Data
Configure consecutive data by combining the MEMOBUS/Modbus register address (test code in case of a loopback test)
and the data the register contains. The data length changes depending on the command details.
A converter MEMOBUS/Modbus register always has a data length of two bytes. Data written into converter registers
must also always have a length of two bytes. Register data read out from the converter will always consist of two bytes.
◆
Error Check
The converter uses a CRC-16 (cyclic redundancy check, checksum method) for checking data validity. Use the procedure
described below when calculating the CRC-16 checksum for command data or when verifying response data.
■
Command Data
When the converter receives data, it calculates the CRC-16 checksum from the data and compares it to the CRC-16 value
received within the message. Both must match before a command is processed.
An initial value of FFFFH (i.e., all 16 bits equal 1) must be used for CRC-16 calculations in the MEMOBUS/Modbus
protocol.
Calculate the CRC-16 checksum using the following steps:
1.
The starting value is FFFFH.
Function
Code
Function Name
Data Length (bytes)
Command Message
Response Message
Minimum
Maximum
Minimum
Maximum
03H
Read MEMOBUS/Modbus registers
8
8
7
37
08H
Loopback test
8
8
8
8
10H
Write to multiple MEMOBUS/Modbus
registers
11
41
8
8
SLAVE ADDRESS
FUNCTION CODE
DATA
ERROR CHECK
