最終更新:2015-02-25 (水) 16:28:59 (2044d)  

STALL
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USB/パケット > USB/ハンドシェイクパケット

概要

  • STALL is returned by a function in response to an IN token or after the data phase of an OUT or in response to a PING transaction.
  • STALL indicates that a function is unable to transmit or receive data, or that a control pipe request is not supported.
  • The state of a function after returning a STALL (for any endpoint except the default endpoint) is undefined.
  • The host is not permitted to return a STALL under any condition.

メモ

  • If an unsupported or invalid request is made to a USB device, the device responds by returning STALL in the Data or Status stage of the request.
  • If the device detects the error in the Setup stage, it is preferred that the device returns STALL at the earlier of the Data or Status stage.
  • Receipt of an unsupported or invalid request does NOT cause the optional Halt feature on the control pipe to be set.
  • If for any reason, the device becomes unable to communicate via its Default Control Pipe due to an error condition, the device must be reset to clear the condition and restart the Default Control Pipe.