2-16
Functional Description
Figure 2-5. Hardware Gate
Data Transfer Modes
You can transfer data from the DAS-1800HC Series boards to the
computer using the following data transfer modes:
●
Interrupt
— You can program the board to generate an interrupt for
events such as
FIFO Half Full
or
FIFO Not Empty
. FIFO Half Full
occurs after the FIFO accumulates 512 12-bit samples for transfer to
computer memory. FIFO Not Empty occurs anytime the FIFO buffer
contains data.
An interrupt occurs in the background, allowing the CPU to execute
other instructions. The interrupt level is software-selectable.
Unpredictable interrupt latencies in the Windows environment tend to
make maximum board speeds unachievable in the interrupt mode.
When in the Windows environment, you are advised to use single- or
dual-channel DMA instead of an interrupt.
1st conversion
2nd conversion
3rd conversion
gate active
gate inactive;
conversions off
gate active;
conversions on
no conversion
Digital trigger
and gate
source
External clock
source
Internal clock
source
1st conversion
2nd conversion
3rd conversion
4th conversion
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