VXI VT1422A - Manual (Page 140)

138 Programming the VT1422A for Data Acquisition and Control Chapter 4
Modifying Running Algorithm Variables
Updating
Algorithm Variables
and Coefficients
The values sent with the ALG:SCALAR and ALG:ARRAY command are
kept in the Update Queue until an ALGorithm:UPDate command is received.
ALG:UPD
cause changes to take place
Updates are performed during phase 2 of the instrument operation cycle
(see Figure 4-7 on page 132). The UPDate:WINDow <num_updates>
command can be used to specify how many updates need to be performed
during phase 2 (UPDATE phase) and assigns a constant window of time to
accomplish all of the updates that will be made. The default value for
<num_updates> is 20. Fewer updates (shorter window) means slightly faster
loop execution times. Each update takes approximately 1.4
μ
s.
To set the Update Window to allow 10 updates in phase 2:
ALG:UPD:WIND 10
allows slightly faster execution
than default of 20 updates
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’
perform updates when bit zero
of VT1533A at channel 133
changes state
For VXIplug&play Users: Use the functions hpe1422_algArray,
hpe1422_algScal to send new values to algorithm variables and
hpe1422_cmd to send the ALG:UPD... SCPI command. See the VT1422A
plug&play driver Help file.
Enabling and
Disabling
Algorithms
An algorithm is enabled by default when it is defined. To enable or disable
an algorithm, use the ALG:STATe <alg_name>, ON | OFF command.
When an individual algorithm is enabled, it executes when the module is
triggered. When disabled, the algorithm does not execute.
NOTE
The command ALG:STATE <alg_name>, ON | OFF does not take effect
until an ALG:UPDATE command is received. This allows multiple
ALG:STATE commands to be sent with a synchronized effect.