Differences between USB Interrupt Transfer and Isochronic Transfer ? RRS feed

  • Question

  • Hi

    If both transfers uses same interval (say: 1ms), what would be the difference? Wouldn't they be equivalent in such case?

    Thanks in advance


    Monday, April 27, 2015 5:04 AM


  • On USB 2.0, interrupt transfers (it is really just polling) have a very limited payload size (64 bytes), and the packet is protected by a CRC. If an error occurs when sending the packet to the hub, it will be retried. Isochronous transfers are much larger (1024 bytes) and will not be retried if there is an error because timeliness is more important than accuracy. So no, they are not equivalent.


    Azius Developer Training Windows device driver, internals, security, & forensics training and consulting. Blog at

    Monday, April 27, 2015 5:16 AM