VTI Instruments Corp.
32
EX1200-1538: Counter/Timer Operation
In
X2
mode, the EX1200-1538 increments/decrements (dependent on which signal leads or lags)
the count on the rising and falling edge of the
Reference
channel (A). As such, each cycle results
in two increments or decrements. X2 mode behavior is shown in Figure 3-21 and X4 behavior is
shown in Figure 3-20.
Logical
Reference
Signal
Logical
Measurement
Signal
3
4
5
6
7
8
9
9
8
7
6
5
4
3
Counter
Value
Incrementing
Decrementing
2
F
IGURE
3-21:
X2
M
ODE
C
OUNTER
I
NCREMENTS
In
X4
mode, the counter increments or decrements similarly on each edge of
Reference
and
Measurement
channels (A and B). Counter increments or decrements depends on which channel
leads the other. Each cycle results in four increments or decrements, increasing the resolution by
four times.
Logical
Reference
Signal
Logical
Measurement
Signal
Incrementing
Decrementing
5
6
7
8
9
10
11
12
13
14
15
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
Counter
Value
16
17
3
4
F
IGURE
3-22:
X4
M
ODE
C
OUNTER
I
NCREMENTS
NOTE
The
results are only for the
Measurement
channel. Hence, the
Reference
channel can be used for
other measurements as well (such as frequency measurements, pulse width, etc.).
