Detecting the presence of a device on a computer system bus by a

Details Detecting the presence of a device on a computer system bus by a Detecting the presence of a device on a computer system bus by a

1994-06-14

1995-11-21

Canney, Vincent P.

Static information storage and retrieval

Magnetic bubbles

Guide structure

36518301, 36518319, G06F 1120

Patent

active

054695546

ABSTRACT:
A computer system determines the presence of a device on the system bus that responds to I/O or memory reads by performing an I/O or memory read with data bus pulled to its normally undriven state. If the value returned is other than the data bus' normally undriven value, it is determined that a device is responsive to that I/O or memory read. Otherwise, the system then pulls the data bus to other than its normally undriven state and performs another I/O or memory read. If the value returned is again the value of the data bus' normally undriven state, it is determined that a device is present because it is driving the data bus back to its normally undriven state. Otherwise, it is determined that a device is not driving the data bus in response to an I/O or memory read. Further, the computer system according to the invention makes the determination of whether a device is driving the bus using a comparator to compare the level present on the data bus in response to the I/O or memory reads.

REFERENCES:
patent: 4999805 (1991-03-01), Culley et al.
patent: 5101492 (1992-03-01), Schultz et al.
patent: 5263148 (1993-11-01), Jones, Jr.
Plug and Play ISA Specification, Version 1.0, May 28, 1993.
EISA Specification, Version 3.1, Appendix 1 of U.S. Pat. No. 5,101,492.

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