Chapter 5
Programming
© National Instruments Corporation
5-15
AT-MIO-64F-5 User Manual
2. Write the mode value to the Am9513A Data Register to store the Counter 2 mode value. Use
one of the following mode values:
8225
Ð Selects 5 MHz clock (Counter 2 Source signal)
8B25 Ð Selects 1 MHz clock
8C25 Ð Selects 100 kHz clock
8D25 Ð Selects 10 kHz clock
8E25 Ð Selects 1 kHz clock
8F25
Ð Selects 100 Hz clock
8525
Ð Selects signal at SOURCE5 input as clock (counts the rising edge of the signal,
6 MHz maximum)
3. Write FF0A to the Am9513A Command Register to select the Counter 2 Load Register.
4. Write 2 to the Am9513A Data Register to store the Counter 2 load value.
5. Write FF42 to the Am9513A Command Register to load Counter 2.
6. Write FFF2 to the Am9513A Command Register to step Counter 2 down to 1.
7. Entries stored in the mux-channel gain memory should be scanned once during a scan
interval. The following condition must be satisfied:
scan interval
³
sample interval *
x
, where
x
is the number of entries in the scan sequence.
Write the desired scan interval to the Am9513A Data Register to store the Counter 2 load
value:
¥
If the scan interval is between 2 and FFFF (65,535 decimal), write the scan interval to the
Am9513A Data Register.
¥
If the scan interval is 10000 (65,536 decimal), write 0 to the Am9513A Data Register.
8. Write FF22 to the Am9513A Command Register to arm Counter 2.
After you complete this programming sequence, Counter 2 is configured to assign a time interval
to scan sequences once the trigger to enable A/D conversions is detected.
Applying a Trigger
Once a data acquisition operation has been configured and programmed, the acquisition
sequence is initiated when a trigger is received. A trigger can be initiated through software or
hardware.
To initiate the data acquisition operation through software, strobe the Start DAQ Register. Make
sure EXTTRIG* is not pulled low at the I/O connector or the RTSI switch.
To initiate the data acquisition operation through hardware, apply an active low pulse to the
EXTTRIG* pin on the AT-MIO-64F-5 I/O connector. See the
Data Acquisition and Analog
Output Timing Connections
section in Chapter 2,
Configuration and Installation
, for
EXTTRIG* signal specifications.
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