3-20
|
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Chapter 3
Hardware Overview
Figure 3-10.
Synchronous Routing Operation
Synchronous routing can be useful for eliminating skew when sending triggers to several
destinations. For example, when sending triggers using the PXI Trigger lines, the trigger arrives
at each slot at a slightly different time. However, if the trigger is sent and received synchronously
using a low-skew synchronization clock, all receiving devices can act on the trigger at the same
time, as shown in Figure 3-11.
Figure 3-11.
Synchronous Routing to Multiple Destinations
Synchronous routing requires the input to be stable at a logic low or logic high state within a
window of time around the clock edge. This window of time around the clock edge is defined
by the setup time (t
setup
) and hold time (t
hold
). If the input signal changes within this window of
time, it is undetermined whether the output of the synchronous route will go to the old or new
logic state. This is important, for example, if a source is being routed synchronously to several
destinations. As shown in Figure 3-12, if the source signal changes within the setup-and-hold
Trigger Inp
u
t
S
ynchroniz
a
tion
Clock
Trigger O
u
tp
u
t
S
et
u
p
Time
t
s
et
u
p
Hold
Time
t
hold
Clock to O
u
tp
u
t
Time, t
CtoQ
PXI_CLK10
Trigger@De
s
tin
a
tion 2
Trigger@De
s
tin
a
tion 1
Trigger O
u
t@
S
o
u
rce
Trigger
S
ynchrono
us
ly Received
@De
s
tin
a
tion
s
1
a
nd 2
A
B
A: Prop
a
g
a
tion del
a
y from
s
o
u
rce to de
s
tin
a
tion 1.
B: Prop
a
g
a
tion del
a
y from
s
o
u
rce to de
s
tin
a
tion 2.
