set up time violations

setup time violation example

if set up time violations occures what will happend
how we can overcome setup time violations

setup violation means

you can not sample data correctly,
there are lots of methods to solve it, for example, modify you code to let signals arrive early, or delay the clock, or decrease your clock frequence

clock with time adjustment

as tarkyss,

The fix for setup violations depends upon which stage of the design flow, the violation has occured.

if it occured during P&R, it can done by rechaning the cell palcement, the cell resizing, clock path delay adjustment..........etc....

If the still the violation exists then u have go back to ur synthesis stage and resynthesis the RTL with better timing constriant or U have restucture you RTL to remove the violations.........

if set-up time violation occure then ur data is not reaching at ur destination flop exactly at one clock cycle.
so to remove set-up time violation you must optimize ur data path delay.

reply if not understand.

Set up time violations means the data is not stable when it is sampled by the next pipeline stage. Be carefor of the critical path.

if setup time violation creeps in .. then u get unknow/undesired/ambigous answer !! ....

to eliminate this violation , adjust timing parameters of input circuitary ..
or expression which related time period of CLOCK, combinational logic, setup time, hold time and skew of clock.

what tool do you use? almost all tools will provide some mechanism to fix set up violation. please refer to the manual.

mostly, setup hold time violation are easily to resolve by P&R if the design does not have so many problems.

setup violation is usually caused by large data path delay.
data path delay is comprised of combinational logic delay and net delay.
firstly,read you sta report to find out which factor above that makes the main delay on setup violation data path.
secondly,if combinational logic delay is the main delay ,you
can make piplining on this combinational logic block ,also you can make some change in you vhdl or verilog code.
find the process that was synthesize to that combinational logic block ,try to decrease the input bit width ,or try to make the input signal more parallel by use () or use case to replace deep nested if-elses.

thirdly ,if the main factor is net delay,you can do some place and route handly in floorplan tools .

Added after 10 seconds:

setup violation is usually caused by data path delay.
data path delay is comprised of combinational logic and net delay.
firstly,read you sta report to find out which factor above that makes the main delay on setup violation data path.
secondly,if combinational logic is the main delay ,you
can make piplining on this block of combinational logic ,also you can change you vhdl or verilog code.
find the process that was synthesize to that combinational logic,try to decrease the input bit width ,or try to make the input signal more parallel by use () or use case to replace deep nested if elses.

thirdly ,if the main factor is net delay,you can do some place and route handly in floorplan tools .

i hope we can specify it by using multicycle paths

shiv_emf said:

if setup time violation creeps in .. then u get unknow/undesired/ambigous answer !! ....

to eliminate this violation , adjust timing parameters of input circuitary ..
or expression which related time period of CLOCK, combinational logic, setup time, hold time and skew of clock.

Click to expand...

Set up Time violation resulted will show that Data launched during the previous cycle is not captured during present cycle.This delay has been due to the Data path delay.Data path delay comprises of Combinational and Net delay.
so ,minimising combi delay will reduce violation.

If the added buffers in combi path ,result violations .These Buffers can be replaced by buffers with high drive strength ,thus reducing number of buffers added and hence delay.
As far as net Delay is concerned it is tool related and more accurate extraction should be used to analyse and minimise it.

Effectively u see ur design failing id setuptime violation is there. Put a high drive strength buffer in tha path where there u see the violation.
Manmohan