Pci bus bridge with transaction forwarding controller for avoiding data

Abstract

A bus bridge which can prevent invalid data from being transferred from a secondary PCI bus to a primary PCI bus even when an SCSI controller or another device provided with a memory the content of which is cleared after a read, is connected to the secondary PCI bus. In a controller, a transaction is processed as a delayed transaction. A combination circuit generates a switching logic signal in accordance with a command or an address included in the transaction. In accordance with the memory content, a bus release controller restricts transmission by a transaction forward controller of a control signal for stopping the transaction issued on the primary PCI bus. Instead of restricting the transmission of the control signal, the time-out period of the buffer memory may be prolonged.