Hach sc100 User Manual page 54

Modbus Protocol
A.6 Modbus Troubleshooting
Problem
No Modus Response
Modbus Exception
Response
Group Name
Measurements
Setup
Setup
Setup
Setup/Analog Output 1
Setup/Analog Output 1
Setup/Analog Output 1
Setup/Analog Output 1
Setup/Analog Output 1
Setup/Analog Output 1
Setup/Analog Output 1
Setup/Analog Output
1/Linear
Setup/Analog Output
1/Linear
54
Table 10 Troubleshooting
Possible Causes
Baud rate, or stop bits does not
match settings of Modbus master
Bad RS232 or RS485 cable
No or improper network biasing and
termination.
Slave Address incorrect or duplicate
address of another bus device.
Register not supported
Data Type incorrect
Table 11 sc100 Modbus Registers
Register
Tag Name
#
Calculated
40001
Value
Language 40003
Date Format 40004
Error Hold
40005
Mode
Source 40006
Sensor
40007
Select
Measuremen
40008
t Select
Type 40009
Transfer
40010
Value
Filter 40012
0mA - 4mA
40013
Select
Min Setting 40014
Max Setting 40016
Solution
Verify sc100 settings match the Modbus master
settings.Verify Modbus master Parity setting is set to
None.
Replace/Repair cable
Check all network devices for termination or biasing
settings. Only the ends of the network should have
termination turned on and only one point on the
network should be providing biasing.
Verify all addresses are unique and between 1 and
247.
Verify register is supported
Verify the requested register(s) Data Type matches the
Modbus Master Request e.g. do not access a Slave
Float value with a 2 byte Integer request. When
requesting a Float (2 registers/4 bytes), both registers
must be requested at the same time.
Data
Length R/W
Type
Float 2 R
Unsigned
1 R/W
Integer
Unsigned
1 R/W
Integer
Unsigned
1 R/W
Integer
Unsigned
1 R/W
Integer
Unsigned
1 R/W
Integer
Unsigned
1 R/W
Integer
Unsigned
1 R/W
Integer
Float 2 R/W
Unsigned
1 R/W
Integer
Unsigned
1 R/W
Integer
Float 2 R/W
Float 2 R/W
Description
Value calculated from two sensor
measurements
Current System Language
Current Data Display Format
(0 = DD/MM/YY; 1 = MM/DD/YY;
2 = DD-MM-YY; 3 = MM-DD-YY)
Error Mode Hold State (0 = Hold
outputs;
1 = Transfer outputs to predefined
value)
Selects data source for this output
(0 = None; 2 = sensor; 4 = Calculation)
Selects sensor source when Source =
Sensor (0 = sensor1; 1 = sensor2)
Selects measurement on the sensor
(0 = Meas1.. 3 = Meas4)
Selects output type
(0 = Linear output; 1 = PID control)
Sets the transfer value
Sets the output filter value in seconds
(0 to 120 sec.)
Selects 0mA/4mA for min output
(0 = 0mA; 1 = 4mA)
Sets the min output value
Sets the max output value