Emerson Micro Motion 3711 Configuration And Use Manual page 155

Modbus Interface
A maximum of twelve records can be returned in one reply. Records are collected until there are no
more unacknowledged records or until the maximum record number is reached, whichever occurs
first.
To access event and alarm logs, a Modbus host program must perform these steps:
1. Send a function code 03 request referencing register 32 (see Table 12-8).
2. Read and interpret the reply. The maximum number of bytes that can be returned is 240
(twelve 20-byte records). See Table 12-9 for the structure of the data field in event log records
and alarm log records. The structure of bytes 1 and 2 in the data field is described in
Table 12-10.
3. Send a function code 05 request referencing register 32 (see Table 12-8) to acknowledge all
records returned in the preceding response.
Note: If events and alarms are not acknowledged, they will be returned in the next response to an
alarm or event log request.
Table 12-8 Modbus event and alarm data requests
Modbus
function code Register bytes
(1)
03 32
(1)
05 32
(1) Default register. Register number may be changed in History Access Registers panel.
Table 12-9 Data field structure for event records and alarm log records
Byte Event log record
1-2 Operator change (Event Log) bit map (16-bit integer).
Refer to Table 12-10.
3-4 Modbus register number of variable (16-bit integer)
5-8 Timestamp (HHMMSS; 32-bit floating point)
9-12 Datestamp (MMDDYY; 32-bit floating point)
13-16 Previous value of variable (32-bit floating point)
17-20 Current (new) value of variable (32-bit floating point)
(1) Calculated as years since 1980. For example, for 2005 the YY value is 25. Note that this is different from the YY value in history data.
Table 12-10 Operator change and alarm change bit maps
Bit Operator change bit map
0 Fixed value – Change to an EU value on an I/O point in Manual Mode Not used
1 Zero scale – Change to the 0% Adjusted on an AO or AI
2 Full scale – Change to the 100% Adjusted on an AO or AI
3 Operator entry work value – Change to any parameter other than
those described above
Configuration and Use Manual
Data field
Data bytes
N/A
N/A
Data field
Alarm log record
Alarm change bit map (16-bit integer).
Refer to Table 12-10.
Modbus register number of variable (16-bit integer)
Timestamp (HHMMSS; 32-bit floating point)
(1)
Datestamp (MMDDYY; 32-bit floating point)
Current (alarmed) value of variable (32-bit floating
point)
Unused (zero filled when transmitted to the master)
Description
Requests unacknowledged event and alarm
records.
Acknowledges all records returned in the
preceding response.
Alarm change bit map
Not used
Not used
Not used
(1)
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