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9.2: Illegal Baud Rate Indexes




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This article is from the Programming VCOMM FAQ, by nelson@desktop.nsc.com (Taed Nelson) with numerous contributions by others.

9.2: Illegal Baud Rate Indexes


[Contributed by Taed Nelson (nelson@lan.nsc.com).]

In a few different circumstances, SetCommState will be asked to use a CBR_
baud rate index of 0xFF00. According to all of the documentation I have seen,
that is clearly an illegal baud rate.

The "proper" thing to do is to return an error of IE_BAUDRATE.

My theory is that this is old behavior that has a special meaning, such as
"set to lowest supported baud rate" or something like that.

One easy way to duplicate this behavior under Windows 95 is to run Modems in
the Control Panel. Click on the Diagnostics tab. Select your virtual COM
port. Click on More Info. One of the calls to SetCommState will have this
illegal case.


 

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