sreerangakumar,

The ATMEL AT89C52 data sheet indicates:

OH Output High-voltage (Ports 1,2,3, ALE, PSEN)
I OH = -60 µA, V CC = 5V ± 10% 2.4 V
I OH = -25 µA 0.75 V CC V
I OH = -10 µA 0.9 V CC V

Output Low-voltage (1) (Ports 1,2,3) I = 1.6 mA 0.45 V.

If you inspect your external device data sheets i'll bet you will derive a max input leakage of -/+ 14 ua. So it looks like you will be able to reliably drive the part to either a valid Hi or lo.

regards,
p