What Bit Order Does NI Serial Use To Transmit Data from the Serial Port?

Updated May 15, 2023

Reported In

Driver

  • NI-VISA
  • NI-Serial

Issue Details

  • What bit order is used to transmit data bytes from the serial port?
  • I'm trying to figure out if the VISA Sub VIs transmits serial data least significant bit first or most significant bit first. Is this a option I can set?

Solution

Data bits are transmitted with the least significant bit first. This is not configurable in software because it is intended to conform to the Serial standard. 

Additional Information

According to the LabVIEW help, Data bits are transmitted upside down and backwards, which means that inverted logic is used and the order of transmission is from least significant bit (LSB) to most significant bit (MSB). This is because LabVIEW is conforming to the Serial standard. 

For example, the letter C = 0x43 (hex) = 01000011 (binary) will be transmitted as 1100001 (the last zero can be ignored).

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