Grundfos CIU 202 Functional Profile And User Manual page 52

14.3.2 CIU 502 Modbus TCP communication faults
Fault
1. The slave does not respond to
telegrams
2. The slave responds with exception
response 0x01 "Invalid function"
3. The slave responds with exception
response 0x02 "Invalid data address"
4. The slave returns data value 0xFFFF
(65535)
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Possible cause
a) Configuration or wiring error
a) The master is trying to use an
unsupported function in CIU 502.
a) 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 between
the blocks.
b) The register address offset may have
been changed from default.
a) 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 Grundfos
product.
b) The Grundfos product is not configured
to show the value or lacks a sensor to
read the value.
Remedy
• Check the visual diagnostics on the
Modbus slave. Normal conditions are that
the Grundfos GENIbus LED2 is
permanently green and that the Modbus
TCP LED1 is off or flashing green. If this
is not fulfilled, see section
14.3.1 LED
status.
• Ensure that the cable between the
Modbus TCP master and the Modbus
slave is connected correctly. See section
7.1 Connecting the ethernet
• Ensure that the slave IP address is
configured correctly, and that the correct
slave IP address is used in the Modbus
master poll. See section
7.3 Setting up
the IP addresses.
See section
8. Modbus function code
overview. Modbus function code overview
for supported function codes. Note that
reading and writing coils is not supported,
so only register functions and diagnostics
will be valid.
Avoid reading or writing invalid data
addresses. Ensure that a block of registers
starting at address X is addressed as X - 1
in Modbus telegrams, according to the
Modbus standard.
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.
See section
9. Modbus register overview
available data.
See section
9.7 Pit data register block
data values that require a sensor.
cable.
for
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