ABB REU 610 Technical Reference Manual page 67

1MRS755972
Voltage Relay
Technical Reference Manual - ANSI Version
To read an event record:
1. Write a preset single register command (function 06) to HR671 using a
selection code as data value.
2. Read the selected fault record (function 04) from HR672, register count 8.
Alternatively, a fault record can be read using one command (function 23)
only.
Selection code 1: reading the oldest unread record
Status register 3 (HR403) informs whether there are unread event records (see
Fig. 5.1.15.2.-2). If there is one or several unread event records, the master
can read the contents using selection code 1.
The event record contains a sequence number which makes it possible for the
master to determine whether one or several unread event records have been
deleted due to overflow by comparing it to the sequence number of the
previously read event record.
The slave keeps track of which event record is currently the oldest unread.
The master can continue reading event records for as long as Status register 3
indicates that there are unread records.
Special case 1: If there are no unread event 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 event record
*
without entering selection code 1 again, the contents of the last read record
is returned.
Selection code 2: reading the oldest stored record
By resetting the read pointer using selection code 2, the master can read the
oldest stored event 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 event record.
Selection code -1...-99
REU 610
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