Semiconductor multi-device system with logic means for controlling the operational mode of a set of input/output data bus drivers

摘要

A semiconductor multi-device system incorporated on a single semiconductor chip is disclosed including a central processing unit, a bus, a plurality of peripherals, a plurality of on-chip data bus drivers connected to selected lines of the bus, and logic means for controlling the operation of the on-chip data bus drivers. The multi-device system of the invention is capable of interacting with off-chip components including an off-chip processing unit and off-chip peripherals. The off-chip components may also include a plurality of off-chip data bus drivers that drive data signals onto and off of an off-chip data bus. The on-chip and off-chip drivers must cooperate in order for data signals to transfer properly between the on-chip and off-chip components. The logic means of the invention is designed so as to minimize the logic necessary to cause the on-chip drivers and the off-chip drivers to cooperate properly. The logic means of the invention is also designed to function properly regardless of whether the on-chip processing unit or the off-chip processing unit is in control of the overall system comprising both on-chip and off-chip components. The logic means is also designed to control the operation of the on-chip drivers in a simple and efficient manner. Thus, a multi-device system is disclosed which is a significant improvement over those of the prior art.