Back to results
US 5,710,779 AGranted
Real time data observation method and apparatus
AssigneeTexas Instruments Incorporated
InventorLee D. Whetsel
Life of this patent
Estimating the term…
Abstract
A scan cell design includes a bypass mode in which the scan input (SI) of the cell is connected directly to the scan output of the cell by a connection that bypasses the scan memory (M1) of the cell.
Claims23
A method of operating a plurality of series-connected scan cells, each scan cell operable to capture and scan signals from a target circuit to be observed, comprising the steps of:
- placing one of the scan cells in an observation mode wherein scanning operation thereof is disabled and wherein a data node thereof which is connected to the target circuit is also connected directly to a scan output of said one scan cell to permit the target circuit to drive the scan output directly via the data node;
- placing another of the scan cells in a bypass mode wherein a scan output thereof is connected directly to a scan input thereof, so that said one scan cell is in the observation mode while said another scan cell is in the bypass mode;
- and
- observing, at the scan output of said another scan cell, signal activity occurring at the data node of said one scan cell while said one scan cell is in the observation mode with scanning operation thereof disabled.
1 more element
A scan cell, comprising:
- a scan input;
- a data input connected to a target circuit to be observed;
- a scan output;
- a memory circuit connected between said scan input and said scan output and also connected between said data input and said scan output;
- and
- said data input directly connectable to said scan output.
3 more elements
Electronic circuitry, comprising:
- a plurality of interconnected circuits, each said circuit including functional circuitry for performing normal operating functions of the circuit, and each said circuit including a scan path for communication with said functional circuitry, said scan path having a scan input and a scan output;
- said scan output of a first said circuit connectable to said scan input of a second said circuit, and said scan output of said second circuit connectable to said scan input of a third said circuit;
- and
- each of said scan outputs of said first and second circuits also connectable to a single node which is separate from said scan inputs of said second and third circuits.
1 more element
A scan cell, comprising:
- a scan input;
- a data input connected to a target circuit to be observed;
- a scan output;
- a memory circuit having an output coupled to said scan output, and having an input;
- a selector connected between said scan input and said memory circuit input and also connected between said data input and said memory circuit input, said selector operable to connect either selected one of said scan input and said data input to said memory circuit input in response to a scan control signal that indicates which of said scan input and said data input is selected for connection to said memory circuit input;
- and
- said scan input directly connectable to said scan output via a direct connection that is independent of said memory circuit, said direct connection including a switch which breaks said direct connection in response to selection of said scan input by said scan control signal.
4 more elements
Dependencies are inferred from the claim text.