MSD Utility Incorrectly Identifies UART Chip

Last reviewed: November 23, 1994
Article ID: Q87450

The information in this article applies to:

Microsoft Windows operating system versions 3.1, 3.11

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.

KBCategory: kbtool
KBSubcategory: wincomm win31
Additional reference words: 3.10 3.11 communications comm serial modem

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Last reviewed: November 23, 1994
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