Modbus User Map - GE 350 Communications Manual

GE
Grid Solutions
SR3 Series Protective Relay Platform
Chapter 9: Using the MODBUS User
Map
SR3 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE
Using the MODBUS User Map
3 Series relay units incorporate a powerful feature called Modbus User Map, that allows
the user to read 125 non-consecutive data records.
A master computer will often have to interrogate continuously several connected slave
relays. If the values being read are "randomly" positioned along the memory map, reading
them may require several transmissions, and this may cause a communications overload.
Data records that are positioned in this manner in the memory map, can be remapped to
the address of an adjacent record in the User Map area, so that they can be accessible to
the master computer with only a single read operation.
To program the map this way, addresses for the required records must be written in the
index area, which is located at the addresses from 40524 (0x020B) to 40648 (0x287).
Only single data from the Actual Values subset can be set in the map. The ranges of
addresses that can be configured in that index area are:
Range1 : 30001 to 30523 (Product Device Code to Internal Fault Cause)
[The address 30302 (Current Security Access Level) cannot be configured.]
Range2 : 30946 to 32036 (Alarm Status 4 to Last Actual Values Register)
The values that correspond to the points provisioned in the User Map index (40524
(0x020B) to 40648 (0x287)) may be read from the Actual Values map area located at the
addresses from 30524 (0x020B) to 30648 (0x0287).
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