retrofit purposes and are not needed for normal installations. Some rescaling features
are redundant at the moment.
3.4.8.1
User definable registers
The Modbus register areas 3X and 4X from 1 to 127 can be compiled freely by the
user. Almost any regular register data in the Modbus memory map can be made to
appear as a register copy in this UDR memory area. The regular Modbus source
register is not moved away from its original location and thus it can be read also from
the original location.
3.4.8.2
User definable bits
The Modbus bit address areas 0X and 1X from bit 16 to 2047 can be freely compiled
by the user. Almost any regular bit data in the Modbus memory map can be made to
appear as a bit data copy in this UDB memory area. The regular Modbus source bit
data are not moved away from their original location and thus they can be read also
from the original location.
The bit 16 is the first valid bit address in the address space because the
register and bit addresses overlap and the register addresses start from
the register location 1. The bit address 16 is the same as register 1, bit
0.
3.4.8.3
Data exceptions
Some exceptions exist for the Modbus source data concerning the UD mapping.
•
None of the system status registers or fixed register structures can appear in the
UD area.
•
UD registers/bits themselves cannot act as source data for other UD data.
•
Modbus source data can only be attached to one UD location.
3.4.8.4
Data properties
The UD data inherits all properties from the source data. This applies to:
•
The memory areas on which the source data are located
•
Data pre-scaling in case of registers
3.4.8.5
Unmapped data locations
It is possible to partially scan unmapped register or bit locations, also known as gaps.
No exception responses are generated. The unmapped locations always return data
value 0.
1MRS757645 B
Section 3
Vendor-specific implementation
620 series
43
Communication Protocol Manual
