Patent ID: 6420898
Filing Date: 2002-07-16
Classification: H03K

Abstract:
A main circuit board structure, comprising:a microprocessor connector ready for a microprocessor to plug in, such that as the microprocessor is plugged into the connector, a microprocessor-type signal is generated; a chipset having an input/output buffer, wherein the input/output buffer is capable of picking up the microprocessor-type signal and configuring the chipset to work under a transmission bus specification suitable for operating the microprocessor; and a transmission line structure for coupling from the input/output buffer of the chipset to the microprocessor connector, wherein the input/output buffer comprises: a coordinating controller; a logic control circuit for receiving the microprocessor-type signal; a first transistor and a second transistor respectively coupled to the logic control circuit and an input/output pad of the input/output buffer, wherein both the first and the second transistors are controlled by the logic control circuit; a first resistor element coupled to a terminal voltage source and a terminal of the first transistor, wherein the first resistor element is controlled by the coordinating controller; a second resistor element coupled to a terminal voltage source and a terminal of the second transistor, wherein the second resistor element is also able to pick up an external control signal for determining its state of conductivity; and a buffer for receiving a signal voltage, an input terminal is connected to a reference voltage, and the signal voltage is compared with the reference voltage to produce an output voltage to the coordinating controller, whereupon the coordinating controller then modifies the resistance of the first resistor element according to the output voltage from the buffer, wherein when the microprocessor-type signal is at a first voltage level, the first transistor and the second resistor element are conductive so that the transmission lines follow the specification of a first transmission bus, whereas when the microprocessor-type signal is at a second voltage level, the first transistor, the second transistor and the first resistor element are all conductive so that the transmission lines follow the specification of a second transmission bus.