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4 EXCEPTION CODES
4 EXCEPTION CODES
Exception codes are error codes that are common to the MODBUS protocol and are stored in the response message when a
slave returns an abnormal response for the request message from the master.
When the master receives an exception code from a slave, perform actions according to the description in this chapter.
The response message format when processing completed with an error is shown below.
Abnormal response function code list
This section lists the abnormal response function codes that are stored in the upper byte of the response message format.
(1) Abnormal response function code
(2) Exception code
Abnormal response function code Function name Details
81H Read coils 'Read coils' completed with an error.
82H Read discrete inputs 'Read discrete inputs' completed with an error.
83H Read holding registers 'Read holding registers' completed with an error.
84H Read input registers 'Read input registers' completed with an error.
85H Write single coil 'Write single coil' completed with an error.
86H Write single register 'Write single holding register' completed with an error.
87H Read exception status 'Read exception status' completed with an error.
88H Page 13 Diagnosis function details 'Diagnostics' completed with an error.
8BH Get communications event counter 'Get communications event counter' completed with
an error.
8CH Get communications event log 'Get communications event log' completed with an
error.
8FH Write multiple coils 'Write multiple coils' completed with an error.
90H Write multiple registers 'Write multiple holding registers' completed with an
error.
91H Report slave ID 'Report slave ID' completed with an error.
94H Read file record 'Read file record' completed with an error.
95H Write file record 'Write file record' completed with an error.
96H Mask write register 'Mask write register' completed with an error.
97H Read/Write multiple registers 'Read/Write multiple registers' completed with an
error.
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