Bently Nevada 3300/01 Series, Operation Manual

Page: 52 / 78

•
Exception Code Exception Condition
1 illegal function in request message
2 Illegal data address in request message
3 Illegal data range in request message
•
•
System Monitor
80175-01
16 PROTOCOL SPECIFICATIONS
MODBUS PROTOCOL EXCEPTION RESPONSES
Error codes will be returned in the response message when the interface receives a message with
an illegal
function, address, or data range.
Example:
An unprotected read is attempted from address 36 which is an illegal address for a register
read request. The reply message returns the exception code 2.
The maximum number of valid register addresses is 36. First valid address is 0, last valid
address is 35.
Point (status) data addresses start at 0 also. The maximum number of valid point addresses
is 36 (3 status points for each of 12 monitors). The last valid status address is 35.
Data requests outside of these ranges will either result in an exception code 2 or exception
code 3 message response. Exception code 3 will occur if the starting address is valid but the
number of registers or points requested results in a data address outside the valid range.
Exception code 2 occurs if the starting register or point address is outside the valid address
range.
45