ABB REM 610 Technical Reference Manual page 70

REM 610
70
Motor Protection Relay
Technical Reference Manual
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. 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 event record (function 04) from HR672, register count 8.
Alternatively, an event 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.
4.1.14.2.-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 will be returned. If the buffer is empty, however, the registers will contain
only zeros. This is the only time when sequence number zero will appear.
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 will be 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.
Note!
Resetting the read pointer will not affect the sequence number of the event record.
Selection code -1...-99
With selection code -1...-99, the master can move backwards from the newest event
as many events as defined by the selection code and read that specific event record.
After this, the master can continue reading the following records using selection
code 1, irrespective of whether they have been read before.
Special case: If there is not as many events in the buffer as specified by the selection
code, the oldest stored event will be read.
Selection code 3
The Modbus event buffer is cleared with selection code 3. Clearing the buffer does
not require any read operation to follow.
1MRS 752263-MUM