United States Patent m
DeRoo et al.
[54] WRITE ONCE READ ONLY REGISTERS
[75] Inventors: David T. DeRoo. St. Joseph; Mark D.
Nicol. Stevensville; Michael P. Krau.
Benton Harbor, all of Mich.
[73] Assignee: Packard Bell NEC. Sacramento. Calif.
[21] Appl. No.: 680,099
[22] Filed: Jul. 12, 1996
Related U.S. Application Data
[60] Continuation of Ser. No. 484,452, Jun. 7,1995, abandoned, which is a division of Ser. No. 220,961, Mar. 25, 1994, abandoned.
[51] Int. Cl.fi G06F 12/14
[52] U.S. CI 395/726; 365/195
[58] Field of Search 395/800, 500.
395/726, 856. 287; 365/228. 189, 189.01.
195
[56] References Cited
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US005764995A
[ii] Patent Number: 5,764,995 [45] Date of Patent: Jun. 9, 1998
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OTHER PUBLICATIONS
80386-33/40 CWB personal computer manual, Mugen. 1990. pp. 1-44.
Press Release: "Zenith Data Systems introduces new class of high-performance modular notebook PCs", May 16, 1994.
Primary Examiner—Mehmet B. Geckil
Attorney, Agent, or Firm—Fitch. Even, Tabin & Flannery
[57] ABSTRACT
The invention provides a simple I/O port which can be used to support a variety of system functions such as a revision, configuration or identification register. This port is provided with a means to be programmable once, upon system power-up so that changes to the port contents are possible, but only under controlled conditions. Once the register has been programmed, it will no longer respond to writes.
8 Claims, 46 Drawing Sheets
