Instruction Manual

Instruction Manual
D103434X012
FOUNDATION fieldbus Communication
November 2014
181
data from sensors and ensure proper writes to the actuator without burdening the function blocks that use the data.
The transducer block also isolates the function block from the specific characteristics of the physical I/O.
Block Modes
All blocks have modes. The mode determines the source of the set point, the destination of the output, how the block
executes, and the relationship between setpoint and output. The block mode is determined by the Block Mode
parameter. It is a structured parameter composed of the attributes actual, target, permitted, and normal. The
following defines each of the attributes.
D Target mode—The Target mode is the mode requested by the user or host system. Only one mode is allowed to be
set and it must be a permitted mode as defined by the permitted attribute of the mode parameter.
D Actual mode—This is the current mode of the block. The actual mode may differ from the target mode due to
operating conditions of the block.
D Permitted mode—The permitted mode defines the modes allowed for the block. This is set by the user or host
system but is restricted by the instrument to modes supported by the instrument for the particular block. Any
change request to the Target or Normal attribute is checked against the permitted attribute to ensure the
requested mode is permitted.
When setting the Permitted mode, there is no check against any of the other attributes (Normal or Target modes).
Therefore, the normal or target mode attributes may have a value that is not permitted because the permitted
attribute was modified after the Normal or Target mode was set. This will have no effect on the instrument until the
user attempts to
modify the Target or Normal mode. At this time these attributes are tested against the Permitted modes, thus the user
cannot change the Normal or Target modes to what was formerly permitted.
D Normal mode—The normal mode is the mode the block should be in during normal operating conditions. The
normal mode is set by the user or host system and can only be set to a permitted mode (see permitted mode). The
user or host system can compare the actual mode to the normal mode and, based on the results, determine if the
block is operating normally.
Table C‐1 lists the modes supported by each block contained in the digital level controller.
Table C‐1. FIELDVUE DLC3020f Block Modes
Block Supported Mode Values
Resource Auto and OOS
Transducer Auto, Manual, and OOS
AO RCas, Cas, Auto, Man, LO
(1)
, IMan
(1)
, and OOS
PID ROut, RCas, Cas, Auto, Man, LO
(1)
, IMan
(1)
, and OOS
ISEL Auto, Man, and OOS
AI Man, Auto, and OOS
DI Auto, Man, and OOS
ARTH Man, OOS, and Auto
1. This mode cannot be specified as a target mode.
Changing the block mode requires accessing the Block Mode parameter. For information on using the host system to
change the block mode via this parameter, see the appropriate host documentation.
Note
A downstream block changing to Out of Service impacts the mode of the upstream block. Refer to the block hierarchy in figure
C‐2.