Computer system having expansion unit

摘要

An analog switch is provided to be connected to the signal lines of a bus of a computer body to be led to an expansion unit. When the signal lines of the bus of the expansion unit are pulled up, a high value is sent to the signal lines of the bus of the computer body. When the signal lines of the bus of the expansion unit are pulled down, a low value is sent to the signal lines of the bus of the computer body. After the potential levels of the signal lines of one bus equal to those of the signal lines of the other bus by the high value or the low value sent, a connection control gate array sets the analog switch on. This can allow the signal lines of both buses to be connected together without causing a transient phenomenon even while the bus cycle is being executed.