Reference Manual
00809-0100-4697, Rev EA
October 2011 Rosemount 848T
www.rosemount.com
Appendix D Function Blocks
Analog Input (AI) Function Block . . . . . . . . . . . . . . . . . . . page D-1
Multiple Analog Input (MAI) Function Block . . . . . . . . . .page D-9
Input Selector Function Block . . . . . . . . . . . . . . . . . . . . . . page D-15
ANALOG INPUT (AI)
FUNCTION BLOCK The Analog Input (AI) function block processes field device measurements
and makes them availabl e to other fun ction blocks. Th e output value from the
AI block is in engineering unit s and contains a status indicating the quality of
the measurement. The measuring device may have several measurements or
derived values available in different channels. Use the channel number to
define the variable that the AI block processes.
The AI block supports alarming, signal scaling, signal filtering, signal status
calculation, mode control, and simulation. In Automatic mode, the block’s
output para meter (OUT) reflects the process variable (PV) value and status.
In Manual mode, OUT may b e set manually. The Manual mode is r eflected on
the output st atus. A discrete output (OUT_D) is provided to indicate whether a
selected alarm cond ition is active. Alarm detection is b ased on the OUT value
and user specified alarm limits. The block execution time is 30 ms.
Out = The block output value and status
Out_D = Discrete output that signals a
selected alarm condition
OUT_D
AI OUT
Table D-1. Analog Input Function Block Parameters
Number Parameter Units Description
01 ST_REV None The revision level of the static data associated with the function block. The
revision value will be incremented each time a static parameter value in the block is
changed.
02 TAG_DESC None The user description of the intended application of the block.
03 STRATEGY None The strategy field can be used to identify a grouping of blocks. This data is not
checked or processed by the block.
04 ALERT_KEY None The identification number of the plant unit. This information may be used in the host
for sorting alarms, etc.
05 MODE_BLK None The actual, target, permitted, and normal modes of the block.
Actual: The mode the “block is currently in”
Target: The mode to “go to”
Permitted: Allowed modes that target may take on
Normal: Most common mode for target
06 BLOCK_ERR None This parameter reflects the error status associated with the hardware or software
components associated with a block. It is a bit string, so that multiple errors may be
shown.
07 PV EU of XD_SCALE The process variable used in block execution.
08 OUT EU of OUT_SCALE
or XD_SCALE if in
direct L_TYPE
The block output value and status.
09 SIMULATE None A group of data that contains the current transducer value and status, the simulated
transducer value and status, and the enable/disable bit.