This IC had become obsolute long time ago ..
It was used in very old serial mouse circuits ..
If, for some reasons, you are using a computer with a COM1 port mouse, the best advice I can give you is to .. throw this computer to a rubbish tip.
Trying to get a COM mouse will probably cost you more then a new computer with all "bla bla bla blu blu blu" s..
Regards,
IanP