Despatch Protocol Plus Modbus Communications - Manual (Page 42)

Chromalox Instruments and Controls
A-51643 Rev. 6 10/06/03 36
No. of Registers Lo $08
CRC $----
Exception Response Format
Field Name RTU Example Data Description
Slave Address $06 Slave number 6
Function $81 Read output status with MSB set
Exception Code $02 Illegal Data Address Exception code
CRC $----
5.4.1 [01] Illegal Function
The function code received in the query is not an allowable action for the slave.
5.4.2 [02] Illegal Data Address
The data address received in the query is invalid or is not accessible due to the current communication
security setting. For queries involving multiple registers, if any address is invalid in the entire query, the
entire query is rejected, no action is taken, and an exception is generated.
5.4.3 [03] Illegal Data Value
The query data field is invalid or contains an illegal value. This exception can occur when the query data
exceeds the maximum or minimum allowable value for a register or the data does not agree with the
query function. For queries involving multiple registers, if any data is invalid, the entire query is rejected,
no data is written, and an exception is generated.