Information Technology Reference
In-Depth Information
Stage1
Stage2
Stage(N1+1)
START(N1+1)
Q=1
START2
START1
Till a First
Crossover
Q=0
Q=0
t1+N1*D1
t1
t1+D1
STOP1
STOP2
STOP(N1+1)
t2
t2
t2
Fig. 3.
Time relationship between the input signals at each stage in the design till a
first crossover
delay stage after a first crossover the STOPi signal transition occurs earlier than
the STARTi signal transition till the second crossover. Hence the delay given to
STOPi is D2 more than the delay given to STARTi till a second crossover takes
place. D2 is the delay range after first crossover. This is shown in Figure 4 where
a second crossover is assumed to have taken place in stage(N1+N2+1). After
second crossover START(N1+N2+1) is given a delay D3 more than the delay
given to the STOP(N1+N2+1). D3 is the delay range after second crossover.
Small value of D3 gives a higher delay measurement resolution.
Stage(N1+N2+2)
Stage(N1+2)
Stage(N1+N2+1)
START(N1+N2+1)
START(N1+N2+2)
Q=0
START(N1+2)
Q=0
Q=1
Till a Second
Crossover
t1+N1*D1−N2*D2+D3
t1+N1*D1−N2*D2
t1+N1*D1−D2
STOP(N1+N2+2)
STOP(N1+2)
STOP(N1+N2+1)
t2
t2
t2
Fig. 4.
Time relationship that exists between the input signals in a delay stage after
a first crossover
In Figure 5 , relation between time difference of input signals in two adjacent
delay stages during third crossover is shown. After the analysis till the third
crossover a mathematical equation (2) can now be derived from Figure 5 which
gives the time difference between START1 and STOP1 signal with D3 measure-
ment resolution. Eq. (4) considers a case for maximum path delay between t1
and t2 when no crossover occurs between two input signals. In (4), N denotes
total number of delay stages in measurement architecture.
t
1+(
N
1
×
D
1)
−
(
N
2
×
D
2) + (
N
3
−
1)
×
D
3
≤
t
2
≤
(2)
t
1+
N
1
×
D
1
−
N
2
×
D
2+
N
3
×
D
3
