# What is lockup latch in DFT?

## What is lockup latch in DFT?

A lock-up latch is a transparent latch used to avoid large clock skew and mitigate the problem in closing hold timing due to large uncommon clock path.

Can latches be part of scan chains explain?

latches are very often part of a scan chain, but most commonly as “lock-up latches” that occur between clock domains, to guard against hold time violations in scan shift mode.

What is clock mixing in DFT?

Majorly, in DFT, we avoid mixing different clocks in the same chain, but if there is a constraint to I/O ports we have to stitch scan flops driven by two different clocks in one chain.

### What are retiming flops in VLSI?

Retiming of a synchronous sequential circuit is a transformation that moves flip-flops through combinational logic without altering the function. We move the destination flip-flop of a critical path backward through its scan multiplexer. This splits the flip-flop into three, one on each input of the multiplexer.

What is clock skew in VLSI?

Clock skew is the timing differences between signals in a clock distribution system. Variation of arrival of clock at destination points in the clock Network.

What is scan flow in DFT?

SCAN is a DFT design technique used in IC Design to increase the overall testability of a circuit. SCAN insertion architecture helps to test each of the logic elements in the IC irrespective of its position by inserting test vectors to device pins.

## What is scan in DFT?

Scan is the first step for inserting DFT(design for testability) architecture in any chip. Thus scan insertion improves the controllability and observability of the sequentially flops.

What is sequential depth?

What is the multi clock domain design?

The difference between the single clock domain and multiple clock domain designs is the phase difference between arrivals of the clock signals. The clock sources CLK1 and CLK2 are different for both the domains and regardless of the same or different frequencies the design is treated as multiple clock domain design.

### What is register retiming?

Register retiming is a circuit optimization technique that moves registers forward or backward across combinational elements in a circuit. The aim of this procedure is to shorten the clock cycle or reduce circuit area.

What is DRV in VLSI?

DRV(Design Rule Violations) and DRC(Design rule check) are the terms used judge the quality of chip in different stages in VLSI Physical Design. DRC: It is actually used for making sure layout of a design must be in accordance with a set of predefined technology rules given by the foundry for manufacturability.

Why do we need scan in DFT?

## What is OCC in VLSI?

On-chip Clock Controllers (OCC) are also known as Scan Clock Controllers (SCC). OCC is the logic inserted on the SOC for controlling clocks during silicon testing on ATE (Automatic test Equipment).

What is compression in DFT?

Scan compression is the most commonly used design-for-test (DFT) architecture for reducing ATPG test application time and test data volume. A traditional compression structure is made up of three distinct blocks: a decompressor, a compressor, and an X-tolerance or X-mask.

Why DFT is required?

Introduction to DFT: Post-production testing is necessary because, the process of manufacturing is not 100% error free. There are defects in silicon which contribute towards the errors introduced in the physical device.

### What is fault grading in DFT?

Fault grading is a procedure that rates testability by relating the number of fabrication defects that can in fact be detected with a test vector set under consideration to the total number of conceivable faults.

What is named capture procedure in DFT?

By using something called “named capture procedures,” the user can specify the functionality and relationships between the internal and external signals. The ATPG tool then uses these relationships to create accurate at-speed test patterns driven by the on-chip clocks.

What is CDC in VLSI?

In digital electronic design a clock domain crossing (CDC), or simply clock crossing, is the traversal of a signal in a synchronous digital circuit from one clock domain into another.

## How do you sync two clock domains?

Common methods for synchronizing data between clock domains are:

1. Using m-FF based synchronizers.
2. Using MUX based synchronizers.
3. Using Handshake signals.
4. Using FIFOs (First In First Out memories).
5. Using Toggle synchronizers.
6. Using Xilinx specific clock domain crossing (CDC) tools.