code is E0…E31 depending on which bit within the register indication is (0…15) and
into which state the indication has changed (0…1).
For example an event code like 23.543 35E23 would mean that event occurred at the
time 23.543 and that register 35 bit 11 (23 div 2) changed to value “1” (23 mod 2).
Register 35 bit 11 corresponds to bit address 571 (35*16+11).
If there are several SPA events pending, the interface responds with maximum 5
events every time.
3.5.6 SPA time synchronization
The master has to send at least one complete time synchronization message WD:
before the IED starts accepting shorter time synchronization messages WT:. The IED
accepts time synchronization on either the SPA broadcast address 900, or on its own
address.
3.5.7 SPA ZC-302 configuration
The following chapters contain information on how to set up Modbus data for SPA-
polling when using SPA ZC-302. Knowledge of the organization of Modbus data
objects in the IED is a prerequisite.
3.5.7.1 Utilization of Modbus user definable area for SPA purposes
The IED Modbus data can be relocated to the user definable Modbus memory area.
Therefore it is possible to build up the packed set of measurands and indications. The
user definable register area can also be accessed from the SPA protocol.
The SPA protocol standard defines that the highest possible SPA channel number is
999. This would correspond to Modbus register address 999. Some SPA Master
applications can however access higher channel numbers than 999. If this is the case,
then the SPA Slave application responds with channel numbers higher than 999. In
Modbus data mapping of this product series there are measurand registers that are as
default located on higher register addresses than 999. If this causes problems in the
SPA communication, then the desired measurands can be remapped to the user
definable register area, thus being located on lower register addresses.
When packing MOM + MCB indication bit pairs into Modbus user definable registers,
it is also possible to map MOM only bits into the same register. To poll the register
using the automatic MOM + MCD bit OR-ing feature, map the MOM only bit to an
even bit location in the register, leaving the corresponding MCD location unmapped.
The OR-ing is done for this bit pair, but since the unused MCD bit is always 0, the
result is always according to the MOM bit state.
If the Modbus indication point is mapped to the user definable Modbus area, then the
possible SPA events from this point come from the original Modbus point location. In
1MRS757645 B Section 3
Vendor-specific implementation
620 series 69
Communication Protocol Manual
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