Expand Memory Addressing Capability of 16-Bit Microprocessor
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Jan-31
The memory addressing capability of a 16-bit microprocessor is inherently limited to 64K. Various schemes have been devised to exceed this natural limit. One known device permits addressing 512K memory. The present embodiment, applied to that device, expands the limit from 512K to 896K, and provides increased reliability and flexibility. Referring to the figure, it is seen that the 512K base memory 1 is fully addressable by known device 2 which generates the necessary 20- bit memory addresses. The figure also shows that, for the present embodiment, the base memory is supplemented by memory extension 3 and shadow (back-up) memory 4. It is further seen that these two 384K supplements are associated with the upper 384K of base memory 1.