National Instruments AT-MIO-64F-5, User Manual

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Programming Chapter 5
AT-MIO-64F-5 User Manual 5-14 © National Instruments Corporation
4. Write the 16 LSBs of the sample count value minus 1 to the Am9513A Data Register to
store the Counter 4 load value.
¥ If the 16 LSBs are all 0, write FFFF.
5. Write FF48 to the Am9513A Command Register to load Counter 4.
6. Write 0 to the Am9513A Data Register to store 0 into the Load Register for Counter 4
reloading.
7. Write FF28 to the Am9513A Command Register to arm Counter 4.
8. Write FF05 to the Am9513A Command Register to select the Counter 5 Mode Register.
9. Write 25 to the Am9513A Data Register to store the Counter 5 mode value.
10. Write FF0D to the Am9513A Command Register to select the Counter 5 Load Register.
11. Take the 16 MSBs of the sample count and complete the following steps:
¥ If the 16 LSBs of the sample count are all 0 or all 0 except for a 1 in the LSB, write the
16 MSBs to the Am9513A Data Register to store the Counter 5 load value.
¥ Otherwise, add 1 to the 16 MSBs of the sample count and write that value to the
Am9513A Data Register to store the Counter 5 load value.
12. Write FF70 to the Am9513A Command Register to load and arm Counter 5.
13. Set the CNT32/16* bit in Command Register 1 to notify the hardware that both Counters 4
and 5 will be used as the sample counter.
After you complete this programming sequence, Counter 4 is configured to count A/D
conversion pulses generated by Counter 3, and Counter 5 decrements every time Counter 4
reaches zero. The data acquisition operation is terminated when Counter 4 and Counter 5 reach
zero.
Programming the Scan-Interval Counter
Counter 2 of the Am9513A Counter/Timer is used as the scan-interval counter. Counter 2 can be
programmed to generate a pulse once every
N counts. N is referred to as the scan interval, which
is the time between successive scan sequences programmed into the mux-channel gain memory.
N can be between 2 and 65,536. One count is equal to the period of the timebase clock used by
the counter. The following clocks are available internal to the Am9513A 5 MHz, 1 MHz,
100 kHz, 10 kHz, 1 kHz, and 100 Hz. In addition, the scan-interval timer can use signals
connected to any of the Am9513A SOURCE input pins.
To program the scan-interval counter, use the following programming sequence. All writes are
16-bit operations. All values given are hexadecimal.
1. Write FF02 to the Am9513A Command Register to select the Counter 2 Mode Register.