Microsoft KB Archive/87450

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MSD Utility Incorrectly Identifies UART Chip

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Q87450

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The information in this article applies to:


 * Microsoft Windows versions 3.1, 3.11

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SUMMARY
When you use the Microsoft Diagnostic Utility (MSD) shipped with Windows 3.1 to identify local COM ports on a personal computer, MSD will erroneously report a 16550AF under &quot;UART Chip Used&quot; when in fact there is no UART (universal asynchronous receiver transmitter) chip or COM port installed at that address. This occurs when a utility, such as SETCOM.COM, or a debug script has been used to create a COM port address in the BIOS data segment for a non-existing COM port.

Other defaults reported by MSD for the non-existing COM port are:

Baud Rate: 1

Parity: Space

Data Bits: 8

Stop Bits: 2

Carrier Detect (CD): Yes

Ring Indicator: (RI): Yes

Clear To Send (CTS): Yes

MORE INFORMATION
The 16550AF chip is a UART chip with a 16-byte character buffer to reduce interrupt overhead and errors during high-speed serial transmissions.

Additional query words: 3.10 3.11 communications comm serial modem

Keywords :

Issue type :

Technology : kbWin3xSearch kbWin310 kbWin311