When Port 0 of AT89C52 connect to D0-D7 of 8255 peripheral interface adapter,
is it necessary to put pull-up resistors on the data bus?
If needed, please tell me the appropriate value for these pull-up resistors.
The reason I ask this question is because I am testing a circuit that use
AT89C52 with 8255, and I feel confusing about it.
When I was testing the circuit by using a program without iteration (loop), the output from
8255 was ok but when I was using loop, the circuit need to be added pull up resistor
in order to gain a correct output.

Thanks.