Communications device without passive pullup components

An apparatus comprising:

• a communication bus circuit including a clock line and a data line;
• a first device coupled to the clock line and the data line;
• and
• a second device coupled to the clock line and the data line, the second device including an active pullup device having a first tristate buffer and a second tristate buffer, the first tristate buffer having an input, an output coupled to the data line, and a node to receive a control signal, the second tristate buffer having an input coupled to the data line, an output, and a node to receive the control signal, wherein a current on the clock line is supplied entirely by the second device.

An apparatus comprising:

• a dual-wire communication bus circuit having a first line to carry a data signal and a second line to carry a clock signal;
• a first device including a first buffer and a second buffer, the first buffer having an input, an output coupled to the first line, and a node directly coupled to a first control line, the second buffer having an input coupled to the first line, and an output, and a node directly coupled to the first control line;
• and
• a second device including a third buffer and a fourth buffer, the third buffer having an input coupled to the first line, an output, and a node directly coupled to a second control line, the fourth buffer having an input, an output coupled to the first line, and a node directly coupled to the second control line.

An apparatus comprising:

• a dual-wire communication bus having a first line to carry a data signal and a second line to carry a clock signal, wherein the dual-wire communication bus lacks a pullup resistor coupled between the first line and a supply voltage, and the dual-wire communication bus lacks a pullup resistor coupled between the second line and the supply voltage;
• a first device including a first buffer and a second buffer, the first buffer having an input, an output coupled to the first line, and a node directly coupled to a first control line, the second buffer having an input, and an output coupled to the second line, and a node directly coupled to the first control line;
• and
• a second device including a third buffer and a fourth buffer, the third buffer having an input coupled to the first line, an output, and a node directly coupled to a second control line, the fourth buffer having an input coupled to the second line, an output, and a node directly coupled to the second control line.