Hardware manual

Chapter2 Connection to a PLC
2-254
FC7 Read exception status
Reading of exception status (Bit 0 to 7 of HR400001)
(Request)
Byte 7 FC (Function code)=07 (HEX)
(Normal response)
Byte 7 FC (Function code)=07 (HEX)
Byte 8 Value of exception status
(Abnormal response)
Byte 7 FC (Function code)= 87 (HEX)
Byte 8 Exception code 01 or 02
(Communication example)
Reading of exception status. The read value is 34 (HEX).
07 => 07 34
The Read exception status function reads the data from the device holding special status
information using the MODBUS/TCP protocol. Since the MICRO/I does not have special
registers, the exception status is read by bit 0 to 7 of HR400001.
12.5.6.5 Exception code
The following table describes the exception codes that are sent upon an abnormal response.
Exception
code
Name Description
01 ILLEGAL
FUNCTION
Indicates that a function code that is not defined by the
MODBUS/TCP protocol or a function code that is not supported
by the MICRO/I is designated.
02 ILLEGAL
DATA
ADDRESS
The address information included in the data is invalid. For
example, when reading the number of read words starting from
the starting reference No. for the read, this exception code is sent
if the data exceeds the maximum address of the device.
03 ILLEGAL
DATA VALUE
The value of the data is invalid. This exception code is also sent
when the number of data is invalid.