No, ur not required to tell the cop ur carrying. I would strongly advise against telling him you are armed.
If they ask then by all means tell them you are armed and show ur permit of course. DO NOT reach for ur weapon. Let HIM reach for it and place ur hands where they can seen.
The problem is once a cop knows that you are armed he is gonna secure that weapon till the stop is over. Which means dropping the magazine and clearing the chamber. Now the cops has to worry about UR gun in his car as well as his own and he knows he has to return it to you.
When the cop returns to ur car to give you the weapon he will give you the gun and magazine seperate since he doesnt want you shooting him now when pissed off you got a ticket.
The law only requires you to have ur permit on you if carrying a weapon. No where does it state you are required to advise the cop you are carrying. If you have no plan on shooting the cop with ur gun then DO NOT advise him you have a gun.
It will only make him nervous and if it was in Bpt, HFD, WTBRY, etc... or any other violent place in the country there will be 10 cop cars there in under a minute making life for you very uncomfortable and will likely result in the cop taking you out and going thru ur car.
Would that be legal? Depends on the circumstances. Usually not but in the cities or areas where gun violence is more common the chance is the cop is going thru ur car whether you like it or not and you can file a complaint later if you feel ur rights were violated.
It's just a poor idea for the law abiding citizen. The system is not perfect but when a passenger or operator is stopped and has a gun (legal or not) that will change the dynamics of the stop completely and make you wish you just kept ur mouth shut and went on with ur business after the stop is over. HTH