"will the assembler will support the following...like placing a port on in CJNE command...

loop: cjne p1,#0,loop"

Oops, I was wrong. I wrote that just before I went to bed. No.

"any hint for detecting which bit is set and then what if more bits are set and some bit go low also."

use JB? or CJNE? or JMP @A+DPTR?

"what does it mean to think in negative logic..?"

The port pins of the 8051 are designed for the assumtion that 1=off, and 0=on. Your question looks like you have hardware connected to the port which uses 1 for on, and 0 for off. Although this will probably work, and nobody is going to put you in jail for it, thinking about 1 as on and 0 as off *will* get you into trouble trying to design circuits around the 8052 in the future.

You sound like you could do with the 8052 "Bible". Look under Links/Interesting sites.