DOCERR: XonLim / XoffLim Control RTS Handshaking Threshold

 Last reviewed: November 19, 1996
Article ID: Q158948
The information in this article applies to:
  • Microsoft Win32 Software Development Kit (SDK) for Windows NT, versions 3.1, 3.5, 3.51, 4.0
  • Microsoft Win32 Software Development Kit (SDK) for Windows 95, version 4.0

SUMMARY

The Win32 SDK documentation states that the RTS handshaking threshold is fixed relative to input buffer size (one half low, three quarters high). This is not correct. These settings are controlled by the XoffLim and XonLim members of the DCB structure.

MORE INFORMATION

The XonLim and XoffLim members of the DCB structure used with the SetCommState API influence flow-control behavior for both software and hardware flow control.

While the member names imply that they only apply to software flow control (Xon / Xoff), they are also used in calculating hardware flow control (RTS/CTS and DSR/DTR) thresholds.

KBCategory: kbprg kbdocerr
KBSubcategory: BseCommApi
Additional reference words: 3.10 3.50 3.51 4.00 kbdss setcommstate dcb
xonlim xofflim



THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Last reviewed: November 19, 1996
© 1998 Microsoft Corporation. All rights reserved. Terms of Use.