National Instruments 653X Manuale Utente
Appendix E
Optimizing Your Transfer Rates
E-2
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Obtaining the Fastest Transfer Rates
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.
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.
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.
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.
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
Device
Direct-Memory Access
AT-DIO-32HS
Supported if system DMA resources available. If you are using
two DMA channels, data transfer is faster.
two DMA channels, data transfer is faster.
DAQCard-6533 for
PCMCIA
PCMCIA
Not supported
PCI-DIO-32HS
PCI-6534
PCI-6534
Supported
PXI-6533
PXI-6534
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.
(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)
Mode/Protocol
Peak Rate (MS/s)