National Instruments NI USB-621x - Manual (Page 131)

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