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field. The receiving device should also make CRC calculation for each of the data (except the
check field) inside the package and compare the results with the check field. Only the same
package will be accepted.
8.2 Abnormal response
If the main station sends an illegal package or asks for an invalid data register, an abnormal data
response will be generated. This abnormal data response is composed of the slave station address,
functional code, trouble code, and check field. When the highest bit of the functional code field
is 1, it means that the data frame is an abnormal response at this time. The table below describes
the meanings of abnormal functional codes:
Trouble code
Description
01H
Illegal operation functional code received.
02H
Illegal register operation or over-long data received.