Patrick McMunn wrote in a message to Ryan Hamilton:
 PM> It's just the revision. There have been, if I'm not mistaken,
 PM> 16550, 16550A, 16550AN, and 16550AFN UARTs, with the 16550AFN UART
 PM> being the most recent (someone said the think the ones with a
 PM> 32-byte buffer are 16650). I'm not sure what the changes in them
 PM> are; I asssume they were some sorts of bug fixes.
The chip revisions are the 16550 and 16550A.  The F refers to a process 
revision and the N to a 40 pin dip package.  A 16550AFV for instance comes in 
a 44 pin PCC package.  AFAIK, National did their damndest to make sure that 
no 16550s were left on the market -- they had some embarassing bugs in the 
FIFO logic.
Regards,
       David
--- timEd/2 1.10+
---------------