Patent US3706974A successfully refreshed from Google Patents.
US3706974A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interface multiplexer
Assignee: International Business Machines Corp
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Filing: 1971-10-27
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Granted: 1972-12-19
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Expires: 1991-10-27
Abstract
Abstract A plurality of devices any one of which can request service by a central controlling unit are interconnected in a loop arrangement by an enabling line. The controlling unit is effectively coupled in parallel to all the devices so that the presence of a service request by one of them will immediately initiate operations that will result in one of the devices being granted service. Each device includes logic circuitry to force it to actuate its leg of the enabling line loop if it was the device granted last service or if it does not have a service request present. The connection of the device to the controlling unit results only if it has a service request and receives an enabling line signal from the device preceding it on the loop. Means for bypassing device requests to read high priority requests can be included as can means to initiate data gating overlapping with the establishing of the servicing connection.
Inventors
- 👤 Robert L Patrick
- 👤 Patrick L Rickard
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 22:52
CPC Classifications
G; G06; G06F; G06F13/00; G06F13/14; G06F13/20; G06F13/32; G06F13/34
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
185 words
A device control circuit for use with one of a plurality of devices which contend for connection to an interface comprising means for receiving a service request signal from the associated said device, means for receiving an acknowledgement signal whenever said interface is available, means responsive to a sequence of receipt of a said acknowledgement signal followed by a signal indicative that said service request is no longer present for storing an indication that said device was granted the last servicing with said interface means for receiving an enabling signal input from the device control circuit associated with another of said devices, means for generating an enabling output signal for coupling to the device control circuit associated with another of said devices if (a) either said last servicing indication is present, or (b) said enabling signal input is received in the absence of a said associated device service request signal, and means responsive to receipt of a said enabling signal input, a said associated device service request signal and a said acknowledgment signal for controlling data communications by the associated said device with said interface.
Claim 2
Independent Claim
185 words
A device control circuit for use with one of a plurality of devices which contend for connection to an interface comprising means for receiving a service request signal from the associated said device, means for receiving an acknowledgement signal whenever said interface is available, means responsive to a sequence of receipt of a said acknowledgement signal followed by a signal indicative that said service request is no longer present for storing an indication that said device was granted the last servicing with said interface means for receiving an enabling signal input from the device control circuit associated with another of said devices, means for generating an enabling output signal for coupling to the device control circuit associated with another of said devices if (a) either said last servicing indication is present, or (b) said enabling signal input is received in the absence of a said associated device service request signal, and means responsive to receipt of a said enabling signal input, a said associated device service request signal and a said acknowledgment signal for controlling data communications by the associated said device with said interface.
Claim 3
Dependent Claim
46 words
The device control circuit in accordance with claim 1 which further includes means responsive tO a signal designating that a last servicing indication has been stored in the device control circuit associated with another said device for removing said last servicing indication from said storing means.
Claim 4
Dependent Claim
58 words
Apparatus in accordance with claim 1 wherein at least one of said device control circuits further includes means responsive to an initializing signal associated with said interface communications for forcing the storing of a said last servicing indication, the others of said device control circuits responding to said initializing signal by clearing the said last servicing indication thereof.
Claim 5
Dependent Claim
90 words
Apparatus in accordance with claim 1 wherein each said device control circuits further includes means for receiving a signal indicative that the associated said device is allocated priority servicing, said enabling output signal generation means further includes means for forcing said enabling output signal if (a) said associated device priority signal is absent, (b) an enabling signal from another device control circuit is received, and (c) a signal is received indicating that at least one other device control circuit which has been allocated priority servicing has a service request signal.
Claim 6
Dependent Claim
55 words
Apparatus in accordance with claim 4 wherein each said device control circuit further includes priority condition indicating means responsive to a said priority servicing allocation signal and a said service request from the said associated device for providing an input to the said enabling output signal generating means of the other said device control circuits.
Claim 7
Dependent Claim
52 words
Apparatus in accordance with claim 5 wherein said interface communication establishing means of each said device control circuit is further responsive to said priority condition indicating means of the associated device and receipt of an enabling signal from said device control circuit associated with another said device for establishing said device/interface communications.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-12-19 | 1976-06-19 | 1976-12-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-12-19 | 1980-06-19 | 1980-12-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-12-19 | 1984-06-19 | 1984-12-19 | $7700.00 | Window Closed / Lapsed |