What code made the church of England the official religion?

There no 'code' as such. From the death of Henry VIII (1547) till Elizabeth I came to the throne in 1558 there was religious chaos in England. In the early years of her reign a compromise, often referred to as the Elizabethan Settlement, was worked out to keep most groups within the Church of England. It tried to steer a middle course between Calvinism and something closer to Catholicism. Various laws were then assed requiring conformity with the settlement and placing those who didn't accept at a disadvantage. For example, everyone was required to attend the parish church or be fined. The more senior Anglican bishops continued to sit in the House of Lords, and so on. (Roman Catholics, who gave allegiance to the Pope, were regarded as beyond the pale).

The Elizabethan Settlement gave England a period of peace in matters of religion, but began to show the first signs of cracking under her successor and under Charles I they became very serious and were one of the key factors leading to the English Civil War.