Active pull up apparatus for a data bus

An active pull up configuration for data bus lines unaffected by integral pull up resistors within subsystems. The present application generally relates to digital systems comprising a plurality of power supply levels and data buses. More particularly, this invention relates to digital system comprising subsystems connected by common buses that require automatic charging of certain buses or lines. In a television signal processing apparatus using an I2C bus and using the present invention according to a exemplary embodiment of the present invention, a first device operative in a first mode of operation and a second device operative in said first mode of operation and a second mode of operation wherein said first circuit and said second circuit are both connected by the I2C bus wherein said each data bus line requiring an active pull up is connected to a first power supply via a first resistor integrated within the first device and connected to a second power supply via a second resistor integrated within said second device. The first resistor is electrically isolated from the first power supply during the second mode of operation and electrically connected to the first power supply during the second mode of operation.