how to connect external RAM to keil p[rocesor ?

I have four answers: datasheet.

Maybe you should count them again...

Keil do not make processors!

Your question has nothing to do with Keil - as Per says, you need to go to the Datasheet for the specific processor to answer these questions.

Note that not all 8051-derivatives support external memory, and not all require an external crystal; again, the Datasheet has the details...

conect the microcontroller, to the ds276 c.i, is a tranceiver rs232, configure the uart to 9600 bps,8,n,1 from basicom o other development software,make the ground common, and conecting tx to rx of te printer to the microcontroller, general , the printers have db25 conector,you will sure is rs232, , the comand is the nex "text" and (13) for enter and skip line, for more information about the conectors you can see pinout.ru, remember, the ground common regards

It might be good for something - but not relevant to this thread!

Maybe this one, instead: http://www.keil.com/forum/docs/thread12762.asp