ADLINK ACL-8216 - Manual (Page 43)

Operation Theorem • 35
4.1.3 A/D Data Transfer Modes
On the ACL-8216, three A/D data transfer modes can be used when the
conversion is completed. The data transfer mode is controlled by the mode
control register (BASE+11). The different transfer modes are specified as
follows:
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 8µs on ACL-8216 card. Hence, after software trigger, the
software can wait for at least 10µs then read the A/D register without polling.
Interrupt Transfer
The ACL-8216 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 useful 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-8216 and the PC’s 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.