Specifications

52 •• C/C++ & DLL Libraries
5.18 _7200_DI_DMA_Start
@ Description
The function will perform digital input N times with DMA data transfer
by using one of the following four sampling modes :
1. pacer trigger (internal timer trigger)
2. external rising edge I_IRQ
3. external falling edge I_IRQ
4. I_REQ & I_ACK handshaking
It will take place in the background which will not stop until the Nth
input data is transferred or your program execute
_7200_DI_DMA_Stop function to stop the process.
After executing this function, it is necessary to check the status of the
operation by using the function _7200_DI_DMA_Status. The PCI-
7200 Bus mastering DMA is different from traditional PC style DMA.
Its description is as follow :
Bus Mastering DMA mode of PCI-7200 :
PCI bus mastering offers the highest possible speed available on the
PCI-7200. When the function _7200_DI_DMA_Start is executed, it
will enable PCI bus master operation. This is conceptually similar to
DMA (Direct Memory Access) transfers in a PC but is really PCI bus
mastering. It does not use an 8237-style DMA controller in the host
computer and therefore isn't blocked in 64K max. groups. PCI-7200
bus mastering works as follows:
1. To set up bus mastering, first do all normal PCI-7200
initialization necessary to control the board in status mode.
This includes testing for the presence of the PCI BIOS,
determining the base addresses, slot number, vendor and
device ID's, I/O or memory, space allocation, etc. Please
make sure your PCI-7200 is plug in a bus master slot,
otherwise this function will not be workable.