NuDAQ ACL-8112 Series, Руководство пользователя

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Operation Theorem
Software Data Transfer
Usually, this mode is used with software A/D trigger mode. After the A/D
conversion is triggered by software, the software should poll the
DRDY
bit until it becomes to high level. Whenever the low byte of A/D data is
read, the
DRDY bit will be cleared to indicate the data is read out.
It is possible to read A/D converted data without polling. The A/D
conversion time will not excess 8
µ
s on ACL-8112 card. Hence, after
software trigger, the software can wait for at least 8
µ
s then read the A/D
register without polling.
Interrupt Transfer
The ACL-8112 provides hardware interrupt capability. Under this mode,
an interrupt signal is generated when the A/D conversion is ended and
the data is ready to be read. It is us eful to combine the interrupt transfer
with the timer pacer trigger mode. Under this mode, the data transfer is
essentially asynchronous with the control software.
When the interrupt transfer is used, you have to set the interrupt IRQ level
by hardware jumper. Please refer section 2.10 for IRQ jumper setting.
After the A/D conversion is completed, a hardware interrupt will be
inserted and its corresponding ISR (Interrupt Service Routine) will be
invoked and executed. The converted data is transferred by the ISR
program.
DMA Transfer
The DMA (Direct Memory Access) allows data to be transferred directly
between the ACL-8112 and the PC memory at the fastest possible rate,
without using any CPU time. The A/D data is automatically transferred to
PC's memory after conversion completed.
The DMA transfer mode is very complex to program. It is recommended
to use the high level program library to operate this card. If you wish to
program the software which can handle the DMA data transfer, please
refer to more information about 8237 DMA controller.
5.2 D/A Conversion
The operation of D/A conversion is more simple than A/D operation. You
only need to write digital values into the D/A data registers and the
corresponding voltage will be output from the AO1 or AO2. Refer to