DOCERR: XonLim / XoffLim Control RTS Handshaking Threshold

ID: Q158948

3.10 3.50 3.51 4.00 WINDOWS NT kbprg kbdocerr

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

Keywords          : kbAPI kbKernBase kbGrpKernBase 
Version           : 3.10 3.50 3.51 4.00
Platform          : NT WINDOWS

Last Reviewed: November 21, 1996