2. Series 8 I/O
Planning and Design
2.7. I/O Link performance specifications
R500
Series 8 I/O User's Guide
37
April 2017
Honeywell
Block names
Data processing
Link Units per
cycle time
Cycle time
Pulse width modulation for
DOCHANNEL
BACKCALC Scanning
1
IOM block's
SCANRATE
Pulse width modulation for
DOCHANNEL
OP Store
1
OP connector's CM
Execution Rate
Digital Input Pulse
Accumulation
IOM Blocks
PV Scanning and
AVRAW Scanning
6.85
IOM block
’s
SCANRATE
Reducing I/O Link traffic
If I/O Link overruns persist, you reduce the I/O Link traffic by performing the following:
Increasing the value of the IOM's Scanning Rate parameter [SCANRATE]
(that is, increasing the time interval between IOM scans)
Increase the Execution Period of Control Modules containing Output Channel blocks
Reducing the number of IOMs configured
Split the IOMs across multiple IOLINKS
Check for presence of an address “Chattering ” alarm events
TIP
Link IDs are only detected on their corresponding modules.
Modules with Link ID 1 cannot detect Link ID 2.
Modules with Link ID 2 cannot detect Link ID 1.
Event collection
Under normal conditions, every IOM configured on the I/O Link, whether primary or
secondary, uses Link Units for event collection. This activity is periodic and can be
accounted for, however; conditions in which numerous events and alarms are generated
are unpredictable and may cause transient I/O Link overruns and delays in display
updates. These transient overruns clear once the rush of events and alarms are collected.
PV and Back calculation scanning
The following I/O parameters are automatically scanned by the C300 as soon as the IOM
block is loaded.
Table 7 I/O parameters scanned when the IOM is loaded