16550 UART FIFO Support under Windows NTLast reviewed: May 5, 1997Article ID: Q103108 |
The information in this article applies to:
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SUMMARYOn COM ports that have a 16550 UART chip, Windows NT will automatically enable FIFO support. To verify this, run Event Viewer and look at the system log. Upon startup, each COM port that has a 16550 UART should generate an event whose source is listed as "Serial." If the FIFO for that port has been enabled, the description of the event will read:
While validating that COM1 was really a serial port, a FIFO was detected. The FIFO will be used. MORE INFORMATIONWhile enabling FIFO does grant a speed advantage when communicating over the serial port, there are several known hardware issues with the 16550 UART that show up when FIFO is enabled:
If you are experiencing data loss with FIFO enabled, there is a utility included on the Windows NT CD-ROM to turn FIFO on and off. The utility is in the SUPPORT\SUPTOOLS\I386 directory and consists of the following three files:
FIFO.CMD - A batch file to turn FIFO on and off FIFO_ON.INI - A data file used to turn FIFO on in registry FIFO_OFF.INI - A data file used to turn FIFO off in registryTo use the utility, either change to the correct directory on the Windows NT CD-ROM drive or copy those three files to another drive and change to the directory they are now in and issue one of the following commands:
FIFO OFF - To turn FIFO support OFF FIFO ON - To turn FIFO support ONIf you cannot access these three files or no longer have them, FIFO support can still be changed in the registry through the following steps:
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