open drain so I provided pull-up resistors on port 0 (EA active high)

Likewise the IRQ (interrupt request output) pin on the RTC is also an open drain output so I have a 10k pull up resistor across this, this would prevent any false re-trigger of the 8052 (maybe caused by a noisey environment on board)

The first quoted paragraph seems to say that the "pull-up resistors on port 0 " are only activew whwn "EA active high". I doubt that is the case.

The open drain interrupt pin is presumably connected to one of the P3 pins which all have an internal pullup. To state that you understand that it should be "this would make a false int less likely"

There is no 'e' in noisy

Erik