10. easyE4 communication Connection to other devices
10.17 Modbus TCP
Exception Code 04 = (Error in server) n.a.**
*For an error message, it is sufficient if only one of the requested addresses is not
unlocked or is invalid.
**A read operation always returns consistent data from the image table, since this
data is protected from other modules by semaphores. In other words, as of this writ-
ing, there is no known criterion for a "read discrete inputs" error in the server.
Read Holding Registers 0x03:
In the event of an error, Modbus TCP will send an error frame.
Fault Code
1 byte
0x83 ; Read Holding Registers
Exception Code
1 byte
02 or 03 or 04
Exception Code 02 = Starting address is invalid, i.e.:
l
0 (the user keeps specifying addresses as one-based addresses)
l
Undefined* (please refer to the "Modbus TCP map" table) or
l
Un-enabled*
Exception Code 03 = The number of inputs is not >= 0x0001 and <= 0x07D0
Exception Code 04 = (Error in server) n.a.**
If no analog I/O is physically present (e.g., analog I/O smart modules missing or
faulty), the image table (values = 0) will still be delivered to the client. No check, no
error message.
*For an error message, it is sufficient if only one of the requested addresses is not
unlocked or is invalid.
**A read operation always returns consistent data from the image table, since this
data is protected from other modules by semaphores. In other words, as of this writ-
ing, there is no known criterion for a "read holding registers" error in the server.
Read Input Registers 0x04:
In the event of an error, Modbus TCP will send an error frame.
Fault Code
1 byte
0x84 ; Read Input Registers
Exception Code
1 byte
02 or 03 or 04
Exception Code 02 = Starting address is invalid, i.e.:
l
0 (the user keeps specifying addresses as one-based addresses)
l
Not defined* or
l
Un-enabled*
Exception Code 03 = The number of inputs is not >= 0x0001 and <= 0x07D0
Exception Code 04 = (Error in server) n.a.**
easyE402/24 MN050009ENEaton.com
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