Apparatus for allowing multiple parallel port devices to share a

Details Apparatus for allowing multiple parallel port devices to share a Apparatus for allowing multiple parallel port devices to share a

1995-12-11

1996-09-10

Barry, Lance Leonard

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

395281, 34082503, 34082506, 364DIG1, 364 2419, 364238, 364235, H04Q 100, G06F 1300

Patent

active

055554369

ABSTRACT:
An apparatus and system which allows multiple parallel port devices to share a single parallel port of a personal computer. The invention uses the parallel port signal called Select.sub.-- In which is activated/de-activated by a program running in the personal computer. When a controller within an attached printer senses that this signal is active, it switches the printer to what is referred to as the on-line state. When the printer controller senses that this signal is inactive, it switches the printer to what is referred to as the off-line state. The present invention uses the Select.sub.-- In signal to distinguish between personal computer accesses to the printer and to other devices which may be attached to the parallel port. When the Select.sub.-- In signal is not active, the present invention uses a command decoder which first determines by a sequence of characters received that a command is being sent over the parallel port, and once that determination is made, decodes the command so that subsequent signals from the parallel port are directed to one of the non-printer devices, the particular one selected depending on the command received.

REFERENCES:
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patent: 5005151 (1991-04-01), Kurkowski
patent: 5060134 (1991-10-01), Hunninghaus
patent: 5107260 (1992-11-01), Meissner et al.
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patent: 5359540 (1994-10-01), Ortiz
Black Box Corporation, Black Box Catalog, Jul. 1985, p. 78.

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