Virtual addressing buffer circuit

Abstract

A virtual addressing buffer circuit has improved address mapping and control flexibility for improved physical resource management and a unique opportunity for forward-compatible system design. The virtual addressing buffer formats the output address utilizing a format register as a combination of the new address bits and the original input address bits. The ability to format the output address enables the user to replace certain address bits without requiring that the entire address be replaced. The virtual addressing buffer controls the output of several command signals to external circuits to indicate how the system should respond to the address output from the virtual addressing buffer. The command signals are controlled by a command register and are output from the virtual addressing buffer only when an address match has been verified. The virtual addressing buffer circuit filters out certain bits of an input address as indicated by a filter register before it verifies that the input address matches a stored address. The bit pattern in the filtering register is not fixed, so any bit location in the input address can be filtered out before the address is verified. Once an address match has been detected, the virtual addressing buffer circuit replaces the entire input address with a new formatted address.