National Instruments NI USB-621x Bus Interface, USB Signal Streams, Data Transfer Methods

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Bus Interface

The bus interface circuitry of M Series devices efficiently moves data between host memory and the measurement and acquisition circuits.

All M Series devices are jumperless for complete plug-and-play operation. The operating system automatically assigns the base address, interrupt levels, and other resources.

NI 621x devices incorporate USB-STC2 technology to implement a

Hi-Speed USB interface.

USB Signal Streams

MSeries USB devices have four fully-independent USB Signal Streams for high-performance transfers of data blocks. One USB Signal Stream is available for each measurement and acquisition block.

•Analog input

•Analog output

•Counter 0

•Counter 1

Data Transfer Methods

The two primary ways to transfer data across the USB bus are USB Signal

Stream and programmed I/O.

USB Signal Stream

USB Signal Stream is a method to transfer data between the device and computer memory using USB bulk transfers without intervention of the microcontroller on the NI device. NI uses USB Signal Stream hardware and software technology to achieve high throughput rates and increase system utilization in USB devices.

© National Instruments Corporation 13-1 NI USB-621x User Manual