National Instruments FP-3000 - Manual (Page 126)

Appendix F Troubleshooting
FieldPoint FP-3000 User Manual F-8 www.ni.com
operator in Lookout to the TRK_IN_D.VALUE of the PID object.
Connect the Pot for the operator in Lookout to TRK_VAL.VALUE .
How long does it take a function block to run on the FP-3000?
This depends on the function block. The following are approximate
maximum execution times in firmware revision 1.
The maximum execution time is a function block parameter. You can read
it from any function block. To view execution times using the NI-FBUS
Configurator, select View»Preferences. Select the Block View tab. Check
the Show Block Information checkbox. Now when you double-click on a
function block, a new tab called Block Information will appear. Look at
the parameter
EXECUTION_TIME on the Block Information tab for the
individual function block. If the number is a hexadecimal number, you can
change it to decimal by right-clicking on it and unchecking
Hexadecimal
Data . This decimal value of this parameter is the execution time in
1/32 ms. (i.e., dividing this number by 32 will give the maximum execution
time in milliseconds).
How Can I Determine FP-3000 Execution Time?
If you are running a PID control loop that is entirely contained on the
FP-3000 (i.e., the AI, PID, and AO blocks are all created on the FP-3000)
with no interaction with an HMI (Human-Machine Interface) software
package (such as Lookout or BridgeVIEW), then you can expect a
minimum 50 Hz control loop. Add the worst-case function block execution
time for each function block in the loop to this minimum. A PID control
loop has one AI, one PID, and one AO block. Together they take 20 ms.
(The maximum execution time of a function block is a function block
parameter you can find in the NI-FBUS Configurator under the Block
Information tab for the individual function block.)
For example, if you want to run 10 PID control loops at 20 ms each, this
will be a total of 200 ms of execution time (one-fifth of a second). You
could run 10 loops as fast as 5 times per second. Be aware that the
Expression block takes significantly longer to execute than other function
blocks and is dependent on the downloaded expression.
AI block 6 ms
DI block 5 ms
DO block 5 ms
AO block 7 ms