"i have tried this but the assemblers give errror for this command"

Waqar,

As I said before the instruction is undocumented. You have to hard code the opcode - there is no official assembler mnemonic.

Be sure to clear the carry bit first though!

Regarding the Panasonic PBX:

I suggest you contact Panasonic and tell them you're having difficulty reverse engineering their product. I understand they are very helpful in such cases - if you give them your full name, address and phone number I wouldn't be surprised if they send a team of engineers round to your house to help you out. Very smart chaps those engineers, they always wear uniforms.