ABB REU 610 Technical Reference Manual page 66

REU 610
66
Voltage Relay
Technical Reference Manual - ANSI Version
The fault record contains a sequence number which makes it possible for the
master to determine whether one or several unread fault records have been
deleted due to overflow. The master compares the sequence number to that of
the previously read fault record.
The slave keeps track of which fault record is currently the oldest unread. The
master can continue reading fault records for as long as Status register 3
indicates that there are unread records.
Special case 1: If there are no unread fault records, the contents of the last
*
read record is returned. If the buffer is empty, however, the registers
contain only zeros. This is the only time when sequence number zero
appears.
Special case 2: If the master tries to read the next unread fault record
*
without entering selection code 1 again, the contents of the last read record
will be returned.
Selection code 2: the master reads the oldest stored record
By resetting the read pointer using selection code 2, the master can read the
oldest stored fault record. After this, the master can continue reading the
following records using selection code 1, irrespective of whether they have
been read before.
Resetting the read pointer does not affect the sequence number
of the fault record.
A master reset, that is, clearing of targets and memorized values
and unlatching of output contacts, clears the fault records, after
which the sequence number starts from 1 again.
Event records
Modbus events are derived from SPA events. With a few exceptions, SPA
events update binary points in the DI and the packed HR area.
Simultaneously, a corresponding Modbus event record is generated. The
event record contains the Modbus DI/CO data point address and the value to
which the point has changed (0 or 1). SPA events lacking a corresponding DI/
CO data point are shown as SPA channel and event code (informative event)
in the event record. The maximum capacity of the Modbus event buffer is 99
events. The time stamp of Modbus events is extended to contain complete
information, from date to millisecond.
1MRS755972