Memory Map Change
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
This article describes a technique for changing a memory map when a machine, such as a display station, accepts a cartridge containing a memory. Fig. 1(A) roughly shows an original memory map for a machine which includes a basic read-only storage (ROS) storing a microcode, for example. Addresses X'00000' ... X'0FFFF' are assigned to the basic ROS. When a cartridge containing another ROS is inserted into the machine, the memory map is changed, as shown in Fig. 1(B). That is, the addresses for the basic ROS are changed to X'20000' ... X'2FFFF'. Thus, both the basic ROS and the cartridge ROS are usable. Fig. 2 shows a part of a chip select logic to cope with the above- mentioned memory map change. If the cartridge is not inserted, "-FLAG" signal is high, thereby enabling a NOR gate 2.