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Enabling and
Disabling
Algorithms
Setting Algorithm
Execution
Frequency
Chapter 3
can be used to specify how many updates you need to perform during phase
2 (UPDATE phase) and assigns a constant window of time to accomplish all
of the updates you will make. The default value for <num_updates> is 20.
Fewer updates (shorter window) means slightly faster loop execution times.
Each update takes approximately 1.4 µseconds.
To set the Update Window to allow 10 updates in phase 2:
ALG:UPD:WIND 10
A way to synchronize variable updates with an external event is to send the
ALGorithm:UPDate:CHANnel '<dig_chan/bit>' command.
•
The <dig_chan/bit> parameter specifies the digital channel/bit that
controls execution of the update operation.
When the ALG:UPD:CHAN command is received, the module checks the
current state of the digital bit. When the bit next changes state, pending
updates are made in the next UPDATE Phase.
ALG:UPD:CHAN 'I133.B0'
An algorithm is enabled by default when it is defined. However, the
ALG:STATe <alg_name>, ON | OFF command is provided to allows you to
enable or disable algorithms. When an individual algorithm is enabled, it
will execute when the module is triggered. When disabled, the algorithm
will not execute.
NOTE
The command ALG:STATE <alg_name>, ON | OFF does not take effect
until an ALG:UPDATE command is received. This allows you to send
multiple ALG:STATE commands and then synchronize their effect.
To enable ALG1 and ALG2, and disable ALG3 and ALG4:
ALG:STATE 'ALG1',ON
ALG:STATE 'ALG2',ON
ALG:STATE 'ALG3',OFF
ALG:STATE 'ALG4',OFF
ALG:UPDATE
The ALGorithm:SCAN:RATio '<alg_name>',<num_trigs> command sets
the number of trigger events that must occur before the next execution of
algorithm <alg_name>. If you wanted PID 'ALG3' to execute only every 20
triggers, you would send ALG:SCAN:RATIO 'ALG3',20, followed by an
ALG:UPDATE command. 'ALG3' would then execute on the first trigger
after INIT, then the 21st, then the 41st, etc. This can be useful to adjust the
allows slightly faster execution
than default of 20 updates
perform updates when bit zero of
HP E1533 at channel 133
changes state
enable algorithm ALG1
enable algorithm ALG2
disable algorithm ALG3
disable algorithm ALG4
changes take effect at next
update phase
Programming the HP E1415 for PID Control
91
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