Grundfos CIU 501 User Manual

14.1.2 CIM/CIU 200 Modbus communication faults
Fault Possible cause Remedy
The slave does not respond to
telegrams.
Configuration or wiring error.
• Check the visual diagnostics on the Modbus slave. Is
the Grundfos GENIbus LED flashing green and the
Modbus LED off or flashing green?
• Ensure that the cable between the Modbus master and
the Modbus slave is connected correctly. See section
CIM 200 Modbus RTU setup for wiring
recommendations.
• Ensure that the slave address is configured correctly,
and that the correct slave address is used in the
Modbus master poll. See section Modbus address
selection for slave address selection.
• Ensure that the transmission speed and stop bit/parity
settings are configured correctly in both master and
slave.
• Ensure that each end of the Modbus trunk cable is
terminated, if necessary. See section Termination
resistor for line termination of the Grundfos slave.
• Ensure that the bus topology for a Modbus network is
correct.
The slave may be in listen-only mode.
Either send a restart communications diagnostics
command, or restart the E-pump manually.
If the holding register of address 00001
"SlaveMinimumReplyDelay" is set too high, the master may
time out before receiving the response from the slave.
Increase the time-out span in the master in order to
communicate.
The slave responds with exception
response 0x01: "Invalid function".
The master is trying to use an unsupported function in the
module or unit.
See section Modbus function code overview for supported
function codes. Note that reading and writing coils are not
supported, so only register functions and diagnostics are
valid.
The slave responds with exception
response 0x02: "Invalid data address".
The master is trying to read or write an invalid data
address. If a master tries to read register addresses that
are not listed in the tables, the slave responds with this
exception response. Some masters may automatically try to
read large blocks in one telegram, which will cause
problems if some of the registers in the block are not
supported. An example would be reading the CIM
configuration and CIM status blocks in one telegram. This is
not possible since there are unused addresses among the
blocks.
• Avoid reading or writing invalid data addresses.
• Make sure that register X is addressed as X - 1 in
Modbus telegrams, according to the Modbus standard.
The register address offset may have been changed from
default.
Read the holding register at address 00002 "Register
Offset" to see if this value is different from 0. If so, write the
value 0 to this address to make the slave return to the
default used in this functional profile.
The slave returns data value 0xFFFF
(65535).
The value is unavailable. A data value of 0xFFFF does not
necessarily indicate an error condition. It means that the
value is unavailable from the E-pump.
See section Modbus register addresses for available data.
The E-pump is not configured to show the value or lacks a
sensor to read the value.
See section Pump data register block for data values that
require a sensor.
The slave does not change Modbus
transmission speed with register 0004.
Configuration error.
Set the transmission speed switches to "Software-defined".
Otherwise, the value in register 0004 is ignored by the
slave.
An invalid value may be set in register 00004.
See section Setting the Modbus transmission speed for
invalid values, and set correct value in register 00004.
Related information
5. CIM 200 Modbus RTU setup
5.1 Setting the Modbus transmission speed
5.3 Modbus address selection
5.4 Termination resistor
8. Modbus function code overview
9.7 Pump data register block
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Grundfos CIU 501 Specifications

General

Brand	Grundfos
Model	CIU 501
Category	Controller
Language	English