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4.4 MODBUS PROTOCOL
With the RS485 Serial Communication option fitted and configured, communication
between a master device and slave instruments via protocol conforming to the
MODBUS industry standard is available.
NOTE: Support for multi-parameter Write operations is limited to
support of the Multi-word Write Function (Number 16) but this permits
writing of one parameter value only per message.
The parameter numbering system divides the parameters into bits and words, each
group being numbered independently.
4.4.1 Bit Pa rame ters
There are up to 11 bit pa rame ters:
OM067-4 November, 2000 4-9
59039
1
8
-DIN Digi tal In di ca tor Sec tion 4
Product Man ual - Vol ume I RS485 Se rial Com mu ni ca tions
Parameter
Alarm 1 Status
Alarm 2 Status
Alarm 3 Status
Alarm 1 Latched
PV Under-range Flag
PV Over-range Flag
Sensor Break Active
Reset Latched Alarm
Reset PV Maximum
Reset PV Minimum
Reset Time Elapsed
No.
1
2
3
4
5
6
7
8
9
10
11
Operation
Read Only
Read Only
Read Only
Read Only
Read Only
Read Only
Read Only
Write Only
Write Only
Write Only
Write Only
Notes
1 = Active
1 = Active
1 = Active
1 = Alarm 1 latched *
1 = Active
1 = Active
1 = Active
* Always returns 0 if Alarm 1 not configured to be latching.