VXI VT1422A - Manual (Page 134)

132 Programming the VT1422A for Data Acquisition and Control Chapter 4
INITiating the Module/Starting Scanning and Algorithms
When the INITiate[:IMMediate] command is sent, the VT1422A builds the
input Scan List from the input channels referenced when an algorithm is
defined with the ALG:DEF command above and from the channels
referenced with the ROUTe:SEQuence:DEFine command. The module also
enters the Waiting For Trigger State. In this state, all that is required to start
a scan and/or run an algorithm is a trigger event for each pass through the
input-calculate-output instrument operation cycle. To initiate the module,
send the command:
INIT
module to Waiting for Trigger
State
When an INIT command is executed, the driver checks several interrelated
settings programmed in the previous steps. If there are conflicts in these
settings an error message is placed in the Error Queue (read with the
SYST:ERR? query). Some examples:
•
If TRIG:SOUR is not TIMer then ARM:SOUR must be IMMediate.
•
The time it would take to execute all algorithms is longer than the
TRIG:TIMER interval currently set.
Starting Scanning
and/or Algorithms
Once the module is INITiated it can accept triggers from any source
specified in TRIG:SOUR.
TRIG:SOUR TIMER
(*RST default)
ARM:SOUR IMM
(*RST default)
INIT
INIT starts Timer triggers
or
TRIG:SOUR TIMER
ARM:SOUR HOLD
INIT
INIT readies module
ARM
ARM starts Timer triggers.
... and the algorithms start to execute.
1
INPUT
from SCP
channels,
analog &
digital
4
OUTPUT
output table
sent to SCP
channels
1
INPUT
from SCP
channels,
analog &
digital
1A
VERIFY
SCAN
and update
scan statue
variables
3
EXECUTE ALGS
execute all enabled algorithms
4
OUTPUT
output table
sent to SCP
channels
2
UPDATE
variables &
algorithms
Trigger Event
Set by ALG:OUTPUT:DELay (if any)
Trigger Event
Figure 4-7. Sequence of Loop Operations