How can we declare an interrupt service routine(ISF) function in keil for 80c51??
Isn't it strange that you don't believe the manual explains this? Or that there might exist lots of sample code that shows how to do it?
And why did you select architecture C251? You mentioned 80C51 on the summary line, which is a different architecture.
it may be because you abbreviate Interrupt Service Routine ISF when you search