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:
Apr. 06, 1999
Filed:
Oct. 21, 1996
John D Kenny, Sunnyvale, CA (US);
Steve Wenlung Chang, Fremont, CA (US);
Emilia Vai-Lun Lei, Fremont, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
An apparatus and method for identifying devices on a passive type bus such as an ISA bus where peripheral devices do not identify themselves to the host CPU. The apparatus and method of the present invention has particular application to systems where more than one passive (e.g., ISA type) bus may be implemented and a host CPU has no indication as to which bus a device is coupled to. The data lines of the bus are tied through a pull-up circuit to a logical high level voltage (V.sub.CC) such that, for example in a sixteen-bit data bus, the output data is FF hexadecimal. When a read request is generated on the bus, the bus controller detects whether the data on the bus changes from FF hexadecimal. If a change is detected, then the address device is present on that bus. If the addressed device outputs a data value of FF hexadecimal, that data value is passed through as valid data.