Clarion car radio needs code everytime I turn ignition off?

I have just replaced a Cassette/radio in 306 with a Cd/radio. Two of the three plugs were fine. The one which goes to the steering wheel controls didn't fit. The problem I have is, everytime I turn off the ignition, when I turn it on again and turn on the radio, I have to put the code in and I have lost all the radio settings.
Any help greatly appreciated.