Reconnecting Through the Serial Port Hangs Pentium Computers

• Microsoft Windows NT operating system version 3.1
• Microsoft Windows NT Advanced Server version 3.1

SYMPTOMS

On a Pentium-based computer, when you start a serial communications program, make a connection, exit the communications program, restart the communications program and attempt to make a connection again, Windows NT stops responding (hangs), requiring a hardware reset.

CAUSE

When SERIAL.SYS attempts to simultaneously put the 16550 UART serial port controller into FIFO mode and clear the data in the receive buffer when it already is in FIFO mode and has data in the buffer, the LSR incorrectly continues to think that there is data in the receive buffer even after you read the data register. This hangs the computer at the hardware level.

STATUS

Microsoft has confirmed this to be a problem in Windows NT and Windows NT Advanced Server version 3.1. This problem has been corrected in the latest U.S. Service Pack for Windows NT and Windows NT Advanced Server version 3.1. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K