VALIDITY CHECKING ARRANGEMENT FOR EXTENDED MEMORY MAPPING OF EXTERNAL DEVICES

摘要

A VALIDITY CHECKING ARRANGEMENT FOR EXTENDED MEMORY MAPPING OF EXTERNAL DEVICES In a telecommunications switching system, a CPU utilizes memory mapped access to a number of duplex external devices and other memories. A validity checking arrangement provides for detecting invalid external device unit numbers for memory mapped accesses by the CPU. In addition, this validity checking arrangement will determine that the CPU's operating software has attempted a memory mapped access with an invalid unit number or that a true hardware fault exists.