4. Functions
CNT-3208M-PE
51
Sampling function
Sampling function
The sampling function obtains count data periodically using the internal or external clock.
Acquired sampling data is transferred to memory on the PC by bus mastering. When the internal clock
is used, sampling can be performed at a maximum of 20 MHz (for sampling of one channel).
If this product fails to gain access to the bus to transfer in time, as bus mastering is used, this product
stops transfer, resulting in an error. Note that it depends on the application activities on the PC whether
continuous transfer can be performed at 20 MHz.
This product can perform sampling in various conditions, depending on the combination of the start,
clock, and stop conditions. For setting sampling conditions, see “Control of sampling” described later in
this section.
Bus mastering
The bus mastering feature of this product executes DMA transfer between this product and the memory
space allocated for the application during PCI bus idle time. For the memory space for the application, a
static area is specified, which is allocated by ordinary variable definition. Under the OSs such as
Windows, the memory space for applications is represented by logical addresses; physical addresses
form noncontiguous address spaces. This product transfers data continuously to these noncontiguous
physical address spaces. Bus mastering by this product enables transfer to up to 64 megabytes of
physical memory space. When the actual area to transfer data to from the PC is set, the memory size
available depends on the type of the OS used and the total amount of physical memory mounted on the
PC.
As memory usage types for bus mastering, batch transfer and ring transfer are available. Batch transfer
is completed when transfer reaches the end of the specified memory area. Ring transfer restarts transfer
from the beginning of the specified memory area when the transfer reaches the end of it. Ring transfer
continued until either the stop condition is satisfied or it is stopped by software.
Interrupt (During bus mastering)
The following interrupt features are available during bus mastering:
-
Generating an interrupt upon completion of transfer of the specified number of data items
-
Generating an interrupt upon completion of transfer
These interrupts can be reported to the application by using the relevant function of “API-CNT(98/PC)”.
If transfer is terminated with an error such as failure to acquire the bus or transfer data in time,
this product stops transfer and generates a transfer completion interrupt. The occurrence of any transfer
error can be detected by checking the status.
Summary of Contents for CNT-3208M-PE
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Page 15: ...1 Before Using the Product 8 CNT 3208M PE ...
Page 30: ...2 Setup CNT 3208M PE 23 3 Click on the End button to finish condition setting Click on End ...
Page 35: ...2 Setup 28 CNT 3208M PE ...
Page 71: ...4 Functions 64 CNT 3208M PE ...
