# US 9,435,861 B2 · Efficient scan latch systems and methods

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- Number: US 9,435,861 B2
- Document ID: US9435861B2
- Status: Granted
- Kind: B2
- Application number: 13/663,379
- Filed: 2012-10-29
- Published: 2014-05-01
- Granted: 2016-09-06
- Earliest claimed: 2012-10-29
- Assignees: NVIDIA Corporation
- Applicants: NVIDIA Corporation
- Inventors: Ilyas Elkin; Ge Yang
- Web page: https://patentgrep.com/patent/US9435861B2

## CPC

- G01R 31/318541: {Scan latches or cell details}
- G01R 31/28: Testing of electronic circuits, e.g. by signal tracer ({EMC, EMP or similar testing of electronic circuits G01R31/002;} testing for short-circuits, discontinuities, leakage or incorrect line connection G01R31/50; checking computers {or computer components} G06F11/00; checking static stores for correct operation G11C29/00 {; testing receivers or transmitters of transmission systems H04B17/00})
- G01R 31/3177: Testing of logic operation, e.g. by logic analysers
- G01R 31/318536: {Scan chain arrangements, e.g. connections, test bus, analog signals}
- G01R 31/318544: {Scanning methods, algorithms and patterns (G01R31/3183 takes precedence)}
- G01R 31/318555: {Control logic}
- G01R 31/318533: {using scanning techniques, e.g. LSSD, Boundary Scan, JTAG}
- G01R 31/318572: {Input/Output interfaces}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

Systems and methods for latches are presented. In one embodiment a system includes scan in propagation component, data propagation component, and control component. The scan in propagation component is operable to select between a scan in value and a recirculation value. The data propagation component is operable to select between a data value and results forwarded from the scan in propagation component, wherein results of the data propagation component are forwarded as the recirculation value to the scan in propagation component. The control component is operable to control an indication of a selection by the scan in propagation component and the data propagation component.

## Claims

### Claim 1

A circuit comprising:
a scan in propagation component operable to select between a scan in value and a recirculation value;
a data propagation component operable to select between a data value and results forwarded from the scan in propagation component, the data value is independent of the scan in value, wherein results of the data propagation component are forwarded as the recirculation logical value that is received at the scan in propagation component; and
a control component for controlling an indication of a selection by the scan in propagation component and the data propagation component.

### Claim 2 (depends on 1)

The circuit of claim 1 wherein the data propagation component is operable to pass input data while avoiding a delay associated with the scan in component.

### Claim 3 (depends on 1)

The circuit of claim 1 wherein the scan in component and data propagation component are operable to introduce a delay to scan input.

### Claim 4 (depends on 1)

The circuit of claim 1 wherein the scan in propagation component is configured in the recirculation path of data propagation component.

### Claim 5 (depends on 1)

The circuit of claim 1 wherein the control component includes a gated clock.

### Claim 6 (depends on 1)

The circuit of claim 1 wherein the scan in propagation component includes a multiplexer and the data propagation component includes a multiplexer.

### Claim 7 (depends on 1)

The circuit of claim 1 wherein the scan in propagation component is included in a keeper.

### Claim 8

A method comprising: receiving a scan enable indication; selecting between a scan input and a recirculation value before choosing between a corresponding data input and results of the selecting, wherein results of a data propagation component are forwarded as the recirculation logical value of the scan input and the data input is independent of the scan input; and
choosing between the corresponding data input and the results of the selecting.

### Claim 9 (depends on 8)

The method of claim 8 wherein data input is forwarded directly to another latch while avoiding another component delay when a choice is the data input.

### Claim 10 (depends on 8)

The method of claim 8 wherein scan input is delayed by another component before forwarding to another latch when a choice is the scan input.

### Claim 11 (depends on 8)

The method of claim 8 wherein the selecting is performed in a recirculation path.

### Claim 12 (depends on 8)

The method of claim 8 wherein the choice of a data input avoids subjection to a parasitic load associated with a selection between a scan input and a recirculation.

### Claim 13 (depends on 8)

The method of claim 8 further comprising controlling said selecting with a gated clock signal.

### Claim 14 (depends on 8)

The method of claim 8 wherein a scan input is forwarded through more multiplexers then a data input.