at89c51...help

CODE1
org 000h
mov p0,#00h
mov p1,#11110111b
bil:jnb p0.0,bil
mov p1,#11100110b
end

CODE2
org 000h
mov p0,#0ffh
mov p1,#11110111b
bil:jnb p0.0,bil
mov p1,#11100110b
end

i want to use p0.0 as an input pin, and when it goes high the data to p1 shud change

when i use code 2, it doesnt work...the data changes without p0.0 getting a high

using code1 works...but ...to make a port an input port...we hav to send all 1's...so what is going wrong???

It appears that codes 1 and 2 are the same. Also, it would be more helpful to other reader's eyes if you include your code like this:

code 1:

CODE 2:

no..there is one difference
mov p0,#0ffh

and in other its

mov p0,#00h

this difference is causing a major difference
the one with p0,#00h is working correctly
why???

Code 2 is correct but you need to pull p0.0 low externally with a switch or a sensor.

you need 10K pullups on port 0

You must install 10K pullups if you are using Port 0 for anything else but addressing. Look at the datasheet.
Looks like the code below should work, as long as you have pullup resistors.