United States Patent [19] [ii] Patent Number: 5,404,450
Szczepanek et al. [45] Date of Patent: Apr. 4,1995
[54] COMMUNICATIONS PROCESSOR SYSTEM WITH CONTROL OF DOWNLOADED TASKS
[75] Inventors: Andre Szczepanek, Bedford, England; Denis R. Beaudoin,
Missouri City, Tex.
[73] Assignee: Texas Instruments Incorporated
[21] Appl. No.: 24,893
[22] Filed: Mar. 1,1993
Related U.S. Application Data
[63] Continuation of Ser. No. 445,066, Dec. 4, 1989, abandoned.
[51] Lit Cl.« G06F 15/16
[52] U.S. Q 395/200; 395/325
[58] Field of Search 395/325, 200
[56] References Cited
U.S. PATENT DOCUMENTS
4,298,934 11/1981 Fischer 364/200
4,488,226 12/1984 Wagner et al 364/200
4,562,539 12/1985 Vince 364/200
4,837,677 6/1989 Burrus, Jr. et al 364/200
5,249,266 9/1993 Dye et al 395/162
Primary Examiner—Thomas G. Black
Assistant Examiner—Peter Y. Wang
Attorney, Agent, or Firm—Robert D. Marshall, Jr.;
James C. Kesterson; Richard L. Donaldson
[57] ABSTRACT
A communications processor system 106 that permits communications task code to be safely downloaded from a host system. Direct access to local memory 156 of the communications processor system 106 is permitted only during a downloading process while system 106 in a reset state. This downloading process is implemented with a special.control register. In user mode, the system 106 controls access to local memory 156 by downloaded task code. Specifically, access is prohibited with respect to privileged memory areas, and is limited to a relatively small predetermined range of addresses with respect to other memory areas. This memory protection process is implemented with a special status register and a number of mapping registers.
14 Claims, 12 Drawing Sheets
10
