In specifying the need for X counters, you need to differentiate whether you need the true functionality of a timer for the accuracy requirements or could you use a timer and a background tasker to run timed events.

From the little specific information on this application, there probably is a way to do it on some 8051s family chips, but it would be only for the experts to attempt.

You would probably increase your probability of success by moving to a move powerful microprocessor. A more technical description of your application and its calculating requirements would be useful in making a recommendation.

Another design consideration is the addition of external digital logic for pre-processing your high speed I/O requirements. If you are realling having a worst-case possibility of 20Kbps on four channels, most of your microprocessor time would be consumed responding to interrupts. Unless the purpose of interrupts is to execute RETI instructions, you would probably be swamped.

Note that there are very quick versons of the 8051... but until we know more, it wouldn't be too useful to suggest them.

-Jay C. Box
( Anyone got a Cray-on-a-Chip? )