Voltage level compensating interface circuit for inter-logic circuit data transmission system

Claim 1

A data signal transmission system in an electronic apparatus comprising: at least two semiconductor logic circuits; said at least two semiconductor logic circuits including: a first semiconductor logic circuit in which an output voltage level of a logic "high" bears a first voltage level; and a second semiconductor logic circuit in which an input voltage level of a logic "high" bears a second voltage level, wherein said second voltage level is higher than said first voltage level; interface circuit means disposed between said at least two semiconductor logic circuits for transferring data signals between said first and second semiconductor logic circuits in either direction; said interface circuit means consisting essentially of: a single signal transmission line interconnecting said first and second semiconductor circuits for transfer of each information bit; pull-up circuit means for pulling up said signal transmission line to a desired voltage level so that when said output voltage level of said first semiconductor logic circuit is a logic "high" the level on said signal transmission line is raised at least to said second voltage level; and a switching element operatively interconnected between said signal transmission line and said pull-up circuit means; and a control system for switching said switching element so that said signal transmission line is connected to said pull-up circuit means only when a said data signal is transferred from said first semiconductor logic circuit to said second semiconductor logic circuit.