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What Is the Status of the Chip Select Lines on USB-8451 on Startup?



Hardware: Industrial Communications>>CAN

Problem:
What is the status of the Chip Select lines on the USB-8451 at power up and device configuration/initialization?

Solution:
Listed below is the status of the Chip Select lines in different situations.
  1. When the device is powered on, the Chip Select lines are set to high-impedance inputs. The voltage at a line is approximately 1.2V.
  2. When using Script API and calling Script Enable SPI VI, the Chip Select lines change from inputs to outputs.

    NOTE: In the Script API, you have to call chip select high or chip select low to decide which state you want the chip select to be in.

  3. When using Script API and calling Script Disable SPI VI, the Chip Select lines go back to their original power-on states (high-impedance inputs).
  4. When using the Basic API, the Chip Select lines are driven high (~3.3V) as soon as the configuration is set using a property note. When the write is called, the Chip Select lines are driven low during communication and driven back up after communication. Chip Select lines  never return to their original state within the Basic API.


Related Links:
KnowledgeBase 3WADAH2W: How to Programmatically Detect USB-8451 I2C/SPI Interfaces
KnowledgeBase 41S9PR5N: Why Do I Get An Error When I Try To Create a VISA Alias For My USB-8451?
KnowledgeBase 421F7CC5: Does the NI-USB-8451 Support 16 Bit Transfers?

Attachments:





Report Date: 12/09/2008
Last Updated: 10/28/2014
Document ID: 4S8B7SLQ

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