Honeywell UDC2500 manual Query, Response, Modbus RTU Data Layer Status Exception Codes

Modbus Read, Write and Override Parameters plus Exception Codes

Query

Example: Internal slave error reading 2 registers starting at address 1820h from slave at slave address 02. 02 03 18 20 00 02 CRC CRC

Response

Example: Return MSB in Function Code byte set with Slave Device Failure (04) in the data field. 02 83 04 CRC CRC

Table 10-21 Modbus RTU Data Layer Status Exception Codes

Exception	Definition	Description
Code
01	Illegal Function	The message received is not an allowable action for
		the addressed device.
02	Illegal Data Address	The address referenced in the function-dependent data
		section of the message is not valid in the addressed
		device.
03	Illegal Data Value	The value referenced at the addressed device location
		is no within range.
04	Slave Device Failure	The addressed device has not been able to process a
		valid message due to a bad device state.
05, 06	Slave Device Busy	The addressed device has ejected a message due to a
		busy state. Retry later.
07	NAK,	The addressed device cannot process the current
	Negative Acknowledge	message. Issue a PROGRAM POLL to obtain device-
		dependent error data.
09	Buffer Overflow	The data to be returned for the requested number of
		registers is greater than the available buffer space.
		Function Code 20 only.

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