The SP5611 is a single chip frequency synthesiser designed for TV tuning systems. Control data is entered in the standard I2C BUS format. The device contains 4 addressable bidirectional open collector ports, one of which is a 3-bit ADC. The information on these ports can be read via the I2C BUS. the device has 4 programmable addresses, programmed by applying a specific input voltage to the P3 address select input. This enables two or more synthesisers to be used in a system.