Instruction Manual

Instruction Manual
D103434X012
Blocks
November 2014
116
D Shed logic never results in a non‐permitted target mode.
D Shed logic never attempts to attain an actual mode of Auto or Cas if that mode is not permitted.
Status Handling
Output or readback fault detection is reflected in the status of PV [7], OUT [9], and BKCAL_OUT [25]. A limited SP [8]
condition is reflected in the BKCAL_OUT [25] status. When simulation is enabled through the SIMULATE [10] attribute,
you can set the value and status for PV [7] and READBACK [16].
When the block is in Cas mode and the CAS_IN [17] input goes bad, the block sheds mode to the next permitted
mode.
Setting the Output
To set the output for the AO block, you must first set the mode to define the manner in which the block determines its
setpoint. In Manual mode the value of the output attribute (OUT [9]) must be set manually by the user, and is
independent of the setpoint. In Automatic mode, OUT [9] is set automatically based on the value specified by the set
point (SP [8]) in engineering units and the I/O Options attribute. In addition, you can limit the SP [8] value and the rate
at which a change in the SP [8] is passed to OUT [9].
In Cascade mode, the cascade input connection (CAS_IN [17]) is used to update the SP [8]. The back calculation
output (BKCAL_OUT [25]) is wired to the back calculation input (BKCAL_IN [27]) of the upstream block that provides
CAS_IN [17]. This provides bumpless transfer on mode changes and windup protection in the upstream block.
Note
You must wire BKCAL_OUT [25] to BKCAL_IN [27] of the upstream block that provides CAS_IN [17]. Otherwise, the AO will not
initialize properly, and the setpoint at CAS_IN [17] will not be passed to OUT [9].
An analog readback value, such as temperature, is shown by the process value (PV [7]) attribute in engineering units.
To support testing, you can enable simulation, which allows you to manually set the channel feedback. There is no
alarm detection in the AO function block.
To select the manner of processing the SP and the channel output value configure the setpoint limiting options, the
tracking options, and the conversion and status calculations.
FB_OPTIONS
When the resource block parameter FB_OPTIONS [43] is enabled Casin goes directly to the transducer block rather
than to OUT. Enable / disable FB_OPTIONS in the resource block. FB_OPTIONS is enabled by default.
FB_OPTIONS, when enabled, alerts you when the device that is providing compensation drops off the segment or goes
bad.
Set Point Selection and Limiting
To select the source of the SP [8] value use the MODE [5] attribute. In Automatic (Auto) mode, the local,
manually‐entered SP [8] is used. In Cascade (Cas) mode, the SP [8] comes from another block through the CAS_IN [17]