Patent US5305443A successfully refreshed from Google Patents.
US5305443A
Expired / Lapsed
US
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Microprocessor with low power bus
Assignee: Nokia Bell Labs
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Filing: 1993-01-22
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Granted: 1994-04-19
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Expires: 2013-01-22
Abstract
Abstract A microprocessor provides a bus state referred to as "loop-back". This state holds the data bus at valid logic levels, without use of resistors, after a read transaction has been completed and there are no pending bus transactions. When this state is entered, the data just read from the data bus is driven back onto the data bus, and the device which had provided the data is placed in the tri-state (high-impedance) condition. This loop-back feature, combined with the fact that all other outputs are held at their previous values, provides for near-zero power dissipation on the bus. The inventive technique avoids the use of pull-up resistors, which are provided on prior art tri-state busses to ensure that the busses do not float and enter the threshold region where high power dissipation occurs.
Inventors
- 👤 Robert T. Franzo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 10:01
CPC Classifications
G; G06; G06F; G06F13/00; G06F13/38; G06F13/40; G06F13/4063; G06F13/4068; G06F13/4072; Y; Y02; Y02D; Y02D10/00
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
187 words
An integrated circuit comprising: a bus master including an output buffer for sending data signals, and an input buffer for receiving data signals, over a bus, and means for requesting data to be sent over said bus, from an external device and means for receiving acknowledgement of the receipt of data sent over said bus from said external device; characterized in that said integrated circuit further comprises means for maintaining in a valid logic state on said bus the last-received data, when said integrated circuit receives the acknowledgement of the receipt of said last-received data and no further bus requests have been sent by said means for requesting data, and further characterized in that said means for maintaining in a valid logic state on said bus the last-received data comprises a multiplexer responsive to said acknowledgement and said bus requests, and having first and second inputs for selectively coupling either a data out signal, or alternatively the output of said input buffer, to the input of said output buffer; and wherein the output of said input buffer is directly connected to the second input of said multiplexer.
Claim 2
Dependent Claim
187 words
An integrated circuit comprising: a bus master including an output buffer for sending data signals, and an input buffer for receiving data signals, over a bus, and means for requesting data to be sent over said bus, from an external device and means for receiving acknowledgement of the receipt of data sent over said bus from said external device; characterized in that said integrated circuit further comprises means for maintaining in a valid logic state on said bus the last-received data, when said integrated circuit receives the acknowledgement of the receipt of said last-received data and no further bus requests have been sent by said means for requesting data, and further characterized in that said means for maintaining in a valid logic state on said bus the last-received data comprises a multiplexer responsive to said acknowledgement and said bus requests, and having first and second inputs for selectively coupling either a data out signal, or alternatively the output of said input buffer, to the input of said output buffer; and wherein the output of said input buffer is directly connected to the second input of said multiplexer.
Claim 3
Dependent Claim
17 words
The integrated circuit of claim 1 wherein said input buffer comprises a field effect transistor input stage.
Claim 4
Dependent Claim
18 words
The integrated circuit of claim 2 wherein said field effect transistor input stage includes a CMOS input buffer.
Claim 5
Dependent Claim
14 words
The invention of claim 1 wherein said bus is external to said integrated circuit.
Claim 6
Dependent Claim
12 words
The invention of claim 4 wherein said bus is a multi-conductor bus.
Claim 7
Dependent Claim
12 words
The invention of claim 4 wherein said bus is a single-conductor bus.
Claim 8
Dependent Claim
163 words
A data system comprising a first master device, a second master device, and a multiplicity of slave devices that communicate over the same bus, wherein the first and second master devices each comprises: an output buffer for sending data signals, and an input buffer for receiving data signals, over said bus, and means for requesting data to be sent over said bus from a slave device, and means for receiving acknowledgement of the transfer of data sent over said bus from said slave device; characterized in that said first and second master devices each further comprises means for maintaining in a valid logic state on said bus the last-received data when acknowledgement of the transfer of said last-received data is received, and no further bus requests have been sent by said means for requesting data; and wherein said data system further comprises arbitration means for choosing which of said first and second master devices has access to said bus at a given time.
Claim 9
Dependent Claim
163 words
A data system comprising a first master device, a second master device, and a multiplicity of slave devices that communicate over the same bus, wherein the first and second master devices each comprises: an output buffer for sending data signals, and an input buffer for receiving data signals, over said bus, and means for requesting data to be sent over said bus from a slave device, and means for receiving acknowledgement of the transfer of data sent over said bus from said slave device; characterized in that said first and second master devices each further comprises means for maintaining in a valid logic state on said bus the last-received data when acknowledgement of the transfer of said last-received data is received, and no further bus requests have been sent by said means for requesting data; and wherein said data system further comprises arbitration means for choosing which of said first and second master devices has access to said bus at a given time.
Claim 10
Dependent Claim
62 words
The data system of claim 7 wherein said output buffer is a tri-state output buffer, and further characterized in that said means for maintaining in a valid logic state on said bus the last-received data comprises a multiplexer having an input directly connected to the output of said input buffer, and having an output coupled to the input of said output buffer.
Claim 11
Dependent Claim
17 words
The data system of claim 7 wherein said input buffer comprises a field effect transistor input stage.
Claim 12
Dependent Claim
18 words
The data system of claim 9 wherein said field effect transistor input stage includes a CMOS input buffer.
Claim 13
Dependent Claim
41 words
The data system of claim 7 wherein said first master device is formed in a first integrated circuit, said second master devices is formed in a second integrated circuit, and said bus is external to said first and second integrated circuit.
Claim 14
Dependent Claim
13 words
The data system of claim 11 wherein said bus is a multi-conductor bus.
Claim 15
Dependent Claim
13 words
The data system of claim 11 wherein said bus is a single-conductor bus.
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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) | 1997-04-18 | 1997-10-18 | 1998-04-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-04-18 | 2001-10-18 | 2002-04-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-04-18 | 2005-10-18 | 2006-04-19 | $7700.00 | Window Closed / Lapsed |