Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

clock skew can cause race conditions ?

Status
Not open for further replies.

viju

Member level 4
Member level 4
Joined
Nov 26, 2006
Messages
71
Helped
16
Reputation
32
Reaction score
9
Trophy points
1,288
Location
Bangalore
Activity points
1,815
Hello,
I have a basic question.
can clock skew cause race conditions ? If so than how ? can some one explain with help of eqations ?
As per my knowledge clock skew can cause hold time violations. Is hold time violations and race conditions are same thing ?

My understanding is as follows.
Case : Two flops with some combo. logic between two of them.

if skew in clock is higher than, ( Tc-q of ff1 + Tcombo. logic ) , then same data which is at o/p of ff1 will propagate to the o/p of 2nd flop with in same clk cycle. (i.e. no flop action will be seen).

Is this scenario is considered as race condition?
Please clear the doubt.

Thank you.
 

U r correct !!!
The scenario tht u have mentioned is the race condition !!!
 

    viju

    Points: 2
    Helpful Answer Positive Rating
Hi Viju,

my 2 cents viju

Scenario from a Timing analysis Tool
Startpoint: flop1
(rising edge-triggered flip-flop clocked by clk1)
Endpoint: flop2
(rising edge-triggered flip-flop clocked by clk1)
Path Group: clk1
Path Type: min

Point Incr Path
-------------------------------------------------------------------------
clock clk1 (rise edge) 0.000 0.000
clock network delay (propagated) 1.500 1.500
flop 1/CP (library flop1 cell name)
0.000 1.500 r
flop 1/Q (library flop1 cell name)
0.220 & 1.720 r
flop 2/D (library flop2 cell name)
0.000 & 1.720 r
data arrival time 1.720

clock clk1 (rise edge) 0.000 0.000
clock network delay (propagated) 1.720 1.720 [Clock tree + ck-q]
flop 2/CP (library flop2 cell name)
1.720 r
library hold time 0.040 1.760
data required time 1.760
--------------------------------------------------------------------------
data required time 1.760
data arrival time -1.720
--------------------------------------------------------------------------
slack (VIOLATED) -0.040

One very important point to be remembered during Timing Analysis
For setup check
"data required time - data arrival time"
For hold check
"data arrival time - data required time"


hope i made it clear and not confused.

For better understanding the concepts of static timing analysis
https://www.vlsichipdesign.com/static_timing_analysis.html

Always Praise the Lord

best regards,
vlsichipdesigner
https://www.vlsichipdesign.com
chip design made easy
 

    viju

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top