YASKAWA GA80U4720ABM, Manual

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6.3 MEMOBUS/Modbus Communications
276 YASKAWA SIEPC71061737B GA800 Drive Technical Reference
Figure 6.7 Message Format
■
Slave Address
Set the slave address of the drive to 00 to FF (Hex.). When the slave address is 00 (Hex), the master sends the
command and all slaves receive the command.
The slave will not send a response message to the master.
■
Function Code
There are five function codes that set commands. Table 6.5 shows the different codes.
Table 6.5 Function Codes
Function Code
(Hex.)
Subfunction Code
(Hex.)
Function
Command Message Response Message
Minimum Data
Length
(byte)
Maximum Data
Length
(byte)
Minimum Data
Length
(byte)
Maximum Data
Length
(byte)
03 -
Read the Description of
Holding Register
8 8 7 37
08 - Loopback Test 8 8 8 8
10 -
Writing to Multiple
Holding Registers
11 41 8 8
5A -
Writing to Multiple
Holding Registers /
Reading the Register
Indicated
11 41 17 17
67
010D
Reading Contents of
Non-Consecutive
Holding Registers
10 248 10 248
010E
Writing to Non-
Consecutive Holding
Registers
14 250 8 8
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Communications Data
Communications data is a series of data that uses the combination of the communications register number and the data
for these registers. The data length changes when the description of the command changes. For a loopback test, it
switches to test code.
The communications register for the drive has a 2-byte length. Data that is written to the register for the drive is
usually 2 bytes. Register data that is read from the drive is also 2 bytes.
■
Error Check
Error check uses the CRC-16 method to detect transmission errors. Use the procedure in this section to calculate
CRC-16.
Command Data
When the drive receives data, it will make sure that there are no errors in the data. The drive uses the procedure below
to calculate CRC-16, then compares that data with the CRC-16 value in the message. If the CRC-16 values do not
agree, the drive will not execute a command message.
When you calculate CRC-16 in MEMOBUS/Modbus communications, make sure that you set the start value as FFFF
(Hex.). All 16 bits must be 1.
Use this procedure to calculate CRC-16: