The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 15, 1997
Filed:
May. 22, 1995
Chinh H Le, Austin, TX (US);
James B Eifert, Austin, TX (US);
Motorola, Inc., Schaumburg, IL (US);
Abstract
A data processor (30) includes a multi-level protection circuit (50) which enables the generation of external control signals. The multi-level protection circuit (50) defines regions of protection (41, 42), which may be nested. The protection circuit (50) checks access cycle attributes such as read or write, supervisor or user, and data or instruction. First (51) and second (54) decoders are associated with each other and define two regions (41, 42) which may overlap. When a CPU (31) accesses a memory location within both regions, the protection attributes of the second decoder (54), at a higher priority level than the first decoder (51), control. If an attempted access violates the programmable protection attributes of the second region (42), then the multi-level protection circuit (50) prevents the access from occurring, even though the access attributes of the first decoder (51) alone would enable the access. The protection circuit (50) thus allows the use of high-density memory or peripheral devices for multiple purposes.