MSD Utility Incorrectly Identifies UART Chip (87450)


The information in this article applies to:

  • Microsoft Windows 3.1
  • Microsoft Windows 3.11
This article was previously published under Q87450

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 "UART Chip Used" 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.
Modification Type:MajorLast Reviewed:10/13/2003
Keywords:KB87450
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