Sunday, March 13, 2016

Basics of Setup and Hold Part - 3

Previous Page>>

Q.1 >> Find
  1. Is there any setup violation in following flop network ?
  2. Maximum frequency at which following flop network work fine ?

T = 100ns (10Mhz)
Tc2q = 10ns
Tpd = 50ns
Ts = 5ns
ANS >>
There is no setup time violation if
Tc2q + Tpd < T - Ts
Tc2q + Tpd = 10 + 50 = 60 ns
T - Ts = 100 - 5 = 95 ns
So 60 < 95 (TRUE)
There is no setup violation.
So to find out maximum frequency or minimum time period at which network work is.
Tc2q + Tpd = Tmin - Ts
10 +  50 =   T  -  5
  T = 50 + 10 + 5   =   65ns
Fmax  = (1000/65) Mhz =   15.38Mhz
--------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------
Q.2 >> Find
  1. Is there any setup and hold violation ?
  2. Maximum frequency at which it work fine ?
ANS >>
  1. To check hold violation in network we take worst hold conditions like -  This network work fine for all condition if maximum clock arrival time is less than minimum data arrival time.


Data Path : D1(min) + D2(min) + Tc2q(min) + Tpd(min) 
Minimum Data Arrival Time :  3 + 3 + 8 + 6 = 20ns

Clock Path : D1(max) + D3(max) + D4(max) + Th
Maximum Data requested Time :  6 + 6 + 6 + 2 = 20ns

Slack = Data Arrival time - Data Requested Time
= 20 - 20 = 0ns

Fortunately, This meet Slack and network will work under this condition.


  1. To check setup violation in network we take worst setup conditions like -  This network work fine for all condition if maximum data arrival time is less than minimum clock arrival time.

Data Path : D1(max) + D2(max) + Tc2q(max) + Tpd(max)
Maximum Data Arrival Time :  6 + 6 + 12 + 9 = 33ns

Clock Path : D1(min) + D3(min) + D4(min) + Tclk - Ts
Minimum Clock Arrival Time :  3 + 3 + 3 + 25 - 5 = 29ns
(Minimum Data requested Time)
Slack = Data requested time - Data arrival time
= 29 - 33
= -4ns

This is HUGE neg. Slack and network will not work under this condition. Now maximum frequency at which network work fine is (Tmin) from following setup timing equation.
D1(max) + D2(max) + Tc2q + Tpd(max) = D1(min) + D3(min) + D4(min) + Tmin - Ts

6 + 6 + 12 + 9 = 3 + 3 + 3 + Tmin - 5
Tmin = 33 - 4 = 29ns
Fmax = (1000/29) Mhz = 34.4Mhz
--------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------


Will add more question soon. 
Please visit again !

1 comment: