Input/output device for connection and disconnection of active lines

(54) INPUT/OUTPUT DEVICE FOR

CONNECTION AND DISCONNECTION OF
ACTIVE LINES

(75) Inventors: Tsutomu Yamada; Kenichi Kurosawa;

Yasuo Kaminaga; Kouji Masui;
Akihiro Ohashi, all of Hitachi (JP)

(73) Assignee: Hitachi, Ltd., Tokyo (JP)

( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.

This patent is subject to a terminal disclaimer.

(21) Appl. No.: 09/499,897

(22) Filed: Feb. 8, 2000

Related U.S. Application Data

(63) Continuation of application No. 09/043,517, filed as application No. PCT/JP95/01955 on Sep. 27, 1995, now Pat. No. 6,038,615.

(51) Int. C I. G06F 13/00

(52) U.S. CI 710/107; 710/102; 710/103;

710/2; 710/62; 710/64; 710/131; 361/58;

361/424

Field of Search 710/101, 102,

710/103, 2, 62, 64, 137; 361/58, 424

(58) (56)

References Cited

U.S. PATENT DOCUMENTS

4,079,440 * 3/1978 Ohnuma et al 361/816

5,272,584 * 12/1993 Austray et al 361/58

5,317,697 * 5/1994 Husak et al 710/103

5,434,752 * 7/1995 Huth et al 361/798

5,530,810 6/1996 Bowman .

5,555,510 9/1996 Verseput .

5,974,490 * 10/1999 Fujimura et al 710/103

5,983,298 * 11/1999 Schultz et al 710/103

6,038,615 * 3/2000 Yamada et al 710/2

FOREIGN PATENT DOCUMENTS

405204507A 8/1993 (JP) .

* cited by examiner

Primary Examiner—Rupal Dharia

(74) Attorney, Agent, or Firm—Antonelli, Terry, Stout & Kraus, LLP

(57) ABSTRACT

There is provided an input/output device having of not exerting any adverse influence on other expansion devices connected to a system bus at the time of insertion or removal. An expansion device 800 comprises an electronic circuit 400 and a MOS switch 300, and is connected to a system bus (BUS) via a connector having long and short pins. The expansion device 800 two power supply systems, namely a stable power supply 250 and an unstable power supply 260. At the time of insertion or removal of the expansion device 800, power is provided to the MOS switch 300 and a high impedance maintaining circuit from the stable power supply via a pair of long pins, so as to reliably place the MOS switch 300 in a high impedance state, inside the expansion device the high impedance maintaining circuit 350 drives an open/close control terminal, and power is provided to the electronic circuit 400 from the unstable power supply 260. At the time of insertion or removal, adverse influence is not exerted on the signal transmission on the system bus, and effects of load variation on the main power supply are reduced.

4 Claims, 9 Drawing Sheets