10
ULVAC CRYOGENICS INCORPORATED
Function Code
: This code tells what kind of action to perform. Functions to read and write
can be specified.
Function Code
Function
Data Type
Notes
0x03
Continuous
reading
16Bit Word
Temperature and
conditions
0x10
Continuous
16Bit Word
Parameter
Data
: Data differs by function code.
If continuous reading is selected, the data comprises Register Address of the device where
reading starts and the number of Registers to read. If continuous writing is selected, the
data comprises Register Address of the device where writing starts, and the number of
Registers to write continuously.
Error Check (CRC):
Checks the validity of the contents to communicate. IF the device is
in communication and is experiencing entanglement or disconnection, such communication
is regarded as invalid. The MBD-D performs Error Check following the CRC-16 method.
The CRC-16 calculation is as follows;
The data to send is divided by generator polynominal to work out the remainder.
generator polynominal
:
X
16
+X
15
+X
2
+1
For detailed information on CRC calculation, refer to Modbus web site at Modbus.org.
Examples of Modbus Communication Protocol
<Continuous reading (0x indicates hexadecimal) example>
Request message from the master
Byte (8)
Response message from the Slave(MBD-D)
Byte (9)
The above example is of the message of continuous reading of two registers from MBD-D
register address of 104(0x68).
Address
Function
Code
Register Address
Number of
Registers
Error Check
0x68
0x03
0x0002
0x0002
0x6CF2
1
1
2
2
2
Address
Function
Code
Response Byte
number
Data
Error Check
0x68
0x03
0x04
0x0B930B81
0x6CF2
1
1
1
4
2
Summary of Contents for MBD-D
Page 2: ......
Page 8: ...F 6 ULVAC CRYOGENICS INCORPORATED This page intentionally left blank...
Page 10: ...IW 2 ULVAC CRYOGENICS INCORPORATED This page intentionally left blank...
Page 28: ...16 ULVAC CRYOGENICS INCORPORATED This page intentionally left balnk...
Page 30: ...CS 2 ULVAC CRYOGENICS INCORPORATED This page intentionally left blank...
Page 32: ...Revision History R 2 ULVAC CRYOGENICS INCORPORATED This page intentionally left blank...