Logic Device Allowing an Efficient Code Patchability
Original Publication Date: 1985-Dec-01
Included in the Prior Art Database: 2005-Feb-19
The different functions performed in the Central Control Unit of computer processors are implemented by logic gates, latches, registers controlled by built-in code, called microcode. This code resides in a Read-Only Memory (ROM) where it can never be modified and in a Read/ Write Random-Access Memory (RAM) where its contents can be modified. A logic device is provided in the microcode addressing mechanism which allows to choose dynamically between the ROM or RAM code. If a design problem or malfunction of the ROM microcode arises, the corrected microcode is stored in the RAM and, by means of the logic device, the operator can then dynamically route the addressing structure to the RAM.