National Instruments 653X Manuale Utente

To achieve the highest transfer rates possible, consider the following:

•

Burst mode is the fastest handshaking protocol. You can further 
increase speed by using short cables.

•

Minimize the number of other I/O devices active in the system. Your 
system bus should be as free as possible from unrelated activity.

•

Use the 6534 devices, which have onboard memory. If you are using a 
6533 device, you can connect it to an external FIFO using the burst 
handshaking protocol and clock data out of the FIFO to the peripheral 
device.

•

Direct-memory access (DMA) transfers are faster than interrupt-driven 
transfers, especially for pattern I/O. Refer to Table E-2 to determine 
whether your device supports DMA transfers. If DMA transfers are 
available, the software will use it by default.

Handshaking Trailing-Edge Pulse

1.8

Handshaking Burst

20

Pattern I/O

20

Table E-2.  Devices That Support Direct-Memory Access (DMA) Transfers

AT-DIO-32HS

Supported if system DMA resources available. If you are using 
two DMA channels, data transfer is faster.

DAQCard-6533 for 
PCMCIA

Not supported

PCI-DIO-32HS
PCI-6534

Supported

PXI-6533
PXI-6534

Supported if device is in a peripheral slot that allows bus arbitration 
(bus mastering). Otherwise, use software to select interrupt-driven 
transfers. PXI chassis have bus arbitration for all slots.

Table E-1.  Peak Transfer Rates Based on Mode and Protocol Used (Continued)