Contec CNT32-4MT, Руководство пользователя

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4. Functions
CNT32-4MT(LPCI)
51
Sampling mode
In the sampling mode, the board samples the count value periodically to load it into memory on the PC
according to the specified internal or external clock. The area of memory to store sampling data is a
maximum of 64 MB (16777216 data items), which is restricted depending on the OS used. In particular,
Windows XP, 2000 allows less memory to be allocated relative to the total amount of physical memory.
For use under such an OS, therefore, the area of memory that can be allocated should be checked with a
sample program.
For the sampling mode, sampling operation conditions must be set as well as counter operation
conditions. For details about sampling, see “Sampling function” described later in this chapter. The
counter start can be synchronized with the sampling start.
Pulse input signal
Sampling clock
Count value
0 1 2 3 4 5 6 7 8 8
Nothing
Sampling value
4
Counter start Counter stop Sampling start Sampling stop
4
Nothing
2
Figure 4.10. Timing chart (Counter-asynchronous sampling mode)
Pulse input signal
Sampling clock
Count value
0 0 1 2 3 4 5 6 7 7
Nothing
Sampling value
0 3
Sampling start Sampling stop
7
Figure 4.11. Timing chart (Counter- synchronous sampling mode)