Since 3µs sounds very slow, are you sure, that nothing other connected to P0, than the 10kOhms against VCC ?
Please watch, an oscilloscope probe add about 100pF. So I use always probes with 1/10 voltage divider inside.


If I connect peripherals to P0 there is no need to insert pull ups. Then to avoid floating inputs any "MOVX" was followed by "MOV P0,#0".


Peter