Modbus Exception Codes - Pepperl+Fuchs IC-KP2-2HB17-2V1D Manual

IC-KP2-2HB17-2V1D
Commands
Cyclic reading and writing of registers:
Writing:
During a cyclic data exchange, the master can transfer the content of a register a number of
times without having to execute the identification command again. If you intend to execute the
unmodified identification command again, change the first four telegram bytes. Use the toggle
bit for this.
Each identification command contains the number of a channel (ident channel). This number is
ignored when MODBUS TCP/IP is used. The channel is defined using the register address.
The ident channel is included in the telegram when the register is read.
Reading:
The IDENTControl Compact transfers the response to an identification command once. Note
that the controller evaluates each telegram transferred via the bus. The CPU cycle of the
controller is faster than the bus cycle. When using enhanced commands, we recommend
employing the following procedure for distinguishing between old and new data:
1. If a telegram is available: Telegram length > 0?
2. Is the reply counter for this telegram different to the previous one?
3. If the status set to 0?
If you have answered yes to all three questions, new data is available.
Timeout:
The timeout time depends on the load on the network you are using. Adopt 1000 ms as a
guide.
Cycle time:
The master must retrieve the data for each channel more frequently than new data is generated
to avoid data loss. Select a cycle time that is suitably short. Monitor the FIFO load register to
determine whether the refresh rate at which the master retrieves the data is sufficiently high.
Note!
Visit http://www.pepperl-fuchs.com to view an example for a PLC program.
7.7.5

MODBUS exception codes

The device issues a response for each MODBUS transaction. The following table contains a list
of possible exception codes:
Code
01
02
03
04
06
0A
Name Description
Illegal function The function code is not 03h, 16h, 17h.
Illegal data address The registers to be written or read are outside of the
defined range.
Illegal data value The number of data sets to be read or written is invalid.
Slave device failure Internal error
Slave device busy A MODBUS master attempts to access a channel that is
already being used by another MODBUS master.
Gateway path The device ID is not 1 or 2.
unavailable
39