YASKAWA V1000 Series

C.4 Message Format
In MEMOBUS 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
FUNCTION CODE
DATA
ERROR CHECK
Some space is required between messages as shown below:
time (s)
command message response message command message
PLC→drive PLC→drivedrive→PLC
24 bit length
H5-06
setting
24 bit length
5 ms or more
Figure C.4 Space Between Messages
u
Slave Address
Set the drive address between 0 and 20 in hexadecimal. If set to 0, commands from the master will be received by all slaves (the drive does not provide
a response when a command has been broadcast to all slave devices).
u
Function Code
The three types of function codes are shown in the table below.
Function Code
(Hexadecimal)
Function Name
Command
Message
Maximum (bytes)
Response Message
Maximum (bytes)
Minimum (bytes) Minimum (bytes)
03H Read memory contents 8 8 7 37
08H Loopback test 8 8 8 8
10H Write to multiple memory registers 11 41 8 8
u
Data
Configure consecutive data by combining the memory register address (test code for a loopback address) and the data the register contains. The data length
changes depending on the command details.
u
Error Check
Errors during communication are detected using CRC-16 (cyclic redundancy check, checksum method). Calculations are performed in the following
order:
1. Although the general default setting for CRC-16 calculations is 0, the default for the MEMOBUS/Modbus protocol should be set to -1 (i.e., all 16 bits
equal 1).
2. Calculate CRC-16 with MSB for the final data as LSB, and the LSB for the slave address as MSB.
3. Be sure to also calculate CRC-16 relative to the response messages, and refer to that CRC-16 value in the response message.
C.4 Message Format
YASKAWA ELECTRIC SIEP C710606 18A YASKAWA AC Drive – V1000 Technical Manual (Preliminary)
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C
MEMOBUS/Modbus Communications