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Example of an exception response
In an exception response, the Slave sets the
most-significant bit (MSB) of the function code to
1. The Slave returns an exception code in the data field.
Command Master - Slave:
Message frame:
Exception response:
Answer Slave - Master:
Reply frame:
ADDRESS 01 hex Slave address 1 hex (= 1)
FUNCTION 04 hex Function 4 hex (= 4)
DATA Starting address HI 17 hex Starting address 1770 hex (= 6000)
Starting address LO 70 hex
No. of registers HI 00 hex Invalid number of registers 0005 hex (= 5)
No. of registers LO 05 hex
ERROR CRC HI 34 hex
CHECK CRC LO 66 hex CRC field 3466 hex (=13414)
01 04 17 70 00 05 34 66
ADDRESS 01 hex Slave address 1 hex (= 1)
FUNCTION 84 hex Most significant bit set to 1
ERROR CODE 04 hex Error code 04 => Slave Device Failure
ERROR CRC HI 42 hex CRC field 42C3 hex (= 17091)
CHECK CRC LO C3 hex
01 84 04 42 C3
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