35
Model S4000TH
8.0 Modbus Interface
8.1 Baud Rate
The baud rate is selectable via the Modbus Communications Interface. The selectable baud
rates are 19200, 9600, 4800, or 2400 bits per second.
8.2 Data Format
The Data Format is selectable via the Modbus Communications Interface. The selectable data
formats are as follows:
Data Bits
Parity
Stop Bit
Format
8 None
1 8-N-1
8
Even
1
8-E-1
8 Odd
1 8-O-1
8
None
2
8-N-2
Table 9: Data Format
8.3 Modbus Read Status Protocol (Query/Response)
8.3.1 Modbus Read Query Message
Byte
Modbus
Range
Referenced to S4000TH
1
st
Slave Address
1-247* (Decimal)
S4000TH ID (Address)
2
nd
Function Code
03
Read Holding Registers
3
rd
Starting Address Hi**
00
Not Used by S4000TH
4
th
Starting Address Lo**
00-FF (Hex)
S4000TH Commands
5
th
No. Of Registers Hi
00
Not Used by S4000TH
6
th
No. Of Registers Lo
01
No. Of 16 Bit Registers
7
th
CRC Lo
00-FF (Hex)
CRC Lo Byte
8
th
CRC Hi
00-FF (Hex)
CRC Hi Byte
*NOTE:
Address 0 is reserved for broadcast mode and will not be supported at this time.
** NOTE:
Start Address can be a maximum of 9999 Address Locations (0000-270E).
8.3.2 Modbus Read Response Message
Byte
Modbus
Range
Referenced to S4000TH
1
st
Slave Address
1-247* (Decimal)
S4000TH ID (Address)
2
nd
Function Code
03
Read Holding Registers
3
rd
Byte Count
02
No. Of Data Bytes
4
th
Data Hi
00-FF (Hex)
S4000TH Hi Byte Status Data
5
th
Data Lo
00-FF (Hex)
S4000TH Lo Byte Status Data
6
th
CRC Lo
00-FF (Hex)
CRC Lo Byte
7
th
CRC Hi
00-FF (Hex)
CRC Hi Byte