Multiple Digital Inputs Mapping; Measurand Registers - ABB 615 Series ANSI Manual

1MAC052634-MB D
3.3.4.1
3.3.5
615/620 series ANSI
Communication Protocol Manual
momentary position bit and the MCD bit of a certain indication point always occur as pairs
in the Modbus memory map.
Observe that the MCD bit states are client dependent. The MCD bit is only reset for the
specific Modbus client that reads it. Thus, other Modbus clients may still receive value one
from the same MCD bit when it is read.
MOM indication changes are captured in the IED's sequential Modbus event buffer.
Additionally, the Modbus event buffer provides a time stamp and chronology of indication
changes.

Multiple digital inputs mapping

Digital inputs related to two-bit DPC or DPS objects, for instance circuit breaker and
disconnectors, have a multiple mapping in the Modbus address space. The objects' open
and close bits are coded as MOM+MCD bit pair entities. The MCD bits reveals if the
object has changed its position several times since the Modbus master last scanned it. In
addition, the open and close bits are also coded using MOM values only, among with a
fault bit. The fault bit is set to "1" when the object is in intermediate (00) or faulty (11)
position.
Table 9: Bit treatment
Bits
Close MOM
Close MCD
Open MOM
Open MCD
:
Close MOM
Open MOM
Faulty position MOM
:
The MOM values are identical in each entity. The MCD bit is only reset if the MOM bit
in the same entity is read.

Measurand registers

The Modbus measurands are located in the Modbus register area. The measurands are
readable from 4X areas.
The formula for calculating the Modbus register value is:
(
= IEC 61850
Modbus value
The range of the original IEC 61850 value can be seen in the Modbus memory map point
list.
Vendor-specific implementation
Treatment
One 2 bit entity
One 2 bit entity
One 1 bit entity
One 1 bit entity
One 1 bit entity
)
× +
Value scaleFactor
Section 3
Offset
(Equation 1)
19