Honeywell Experion PKS Series A, User Manual, Page: 61 / 560

3. Fieldbus Integration With Experion System
3.3. Control Mode Interaction
R400 Experion PKS Series A Fieldbus Interface Module User's Guide 61
July 2010 Honeywell
Rotary Switch Model versus Toggle Switch Model
The Fieldbus Foundation supports both the Rotary Switch and the Toggle Switch models
of mode operation. The Rotary Switch model supports only one mode request at a time.
For example, an operator can request OOS, Man, Auto, Cas, RCas, or ROut. It has no
memory of previous target modes.
The Toggle Switch model supports more than one mode request at a time. For example,
an operator can request Manual override of Cascade, Manual override of Remote
Cascade, and so on.
Experion supports the Rotary Switch model as well as the following two instances of the
Toggle Switch model.
An operator may request the Cas mode at the same time the RCas mode is requested
An operator may request the Cas mode at the same time the ROut mode is requested
Experion also ignores the following illegal mode combinations as defined by the
Fieldbus Foundation.
If ROut is set, RCas may not be set. If it is set, it will be ignored.
The Auto and Man bits must always be of opposite states. If neither Auto nor Man or
both are set, and the ROut, RCas, or Cas mode is set, Auto mode will be assumed
with Man cleared. Likewise, If neither Auto nor Man or both are set, and neither
ROut, RCas, nor Cas mode is set, Man mode will be assumed with Auto cleared. For
the OOS mode, the Man bit should be set unless it is not permitted. If Man is not
permitted, the Auto bit should be set unless it is not permitted. If neither Auto nor
Man is permitted, the OOS bit should be set.
ATTENTION
An operator needs an access level of ENGR or higher to invoke the OOS
mode or to return a block to an in-service mode.
The Experion system adheres to the following additional rules for setting fieldbus target
mode bits for its MODE supported subset of combinations.
Fieldbus
Mode
Rule
OOS When setting as the target mode, obtain the target mode, preserve the
Auto and Man bits, set the OOS bit, and optionally reset all the other bits.
Reject the request, if the access level is not ENGR or higher.