Programmable digital memory circuit
US4319343A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 16, 1980 |
| Grant date | Mar 9, 1982 |
| Priority date | — |
| Expiry date | Jul 16, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F8/66
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A programmable digital memory circuit uses a programmable read only memory (PROM) to correct code errors and permit expansion to additional PROM chips. Each code correction or expansion is made via enabling a portion of an overlay patch programmable read only memory (PROM) for a similar portion of the memory circuit at an address code burned into the overlay trap (PROM). Initially the overlay trap PROM is unprogrammed, and each bit location therein can act as an enable/disable selection to a 32 byte block in the overlay patch PROM. When a bit in the overlay trap PROM is programmed and when the memory address selects that location, the main memory is unselected and the patch PROM location is selected, i.e., substituted. The 256 bit locations in the overlay trap PROM can select 256 32 byte patches in the patch PROM for substitution in the main memory. Each patch may be added simply by burning one more location in the overlay trap PROM and inserting the corrected code data into the overlay patch PROM at the corresponding location. In addition to the overlay capability, the memory circuit allows each integrated circuit (IC) memory chip socket on a printed circuit broad to be individual…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.