Overview 1-7
Series
505 High Speed Counter
and Encoder Module User
’
s Manual
1.5 Counting Modes
1.5.1
Pulse
Counter
Each channel has two inputs, A and B. In the pulse counter mode, counting
Mode
occurs on the rising or falling edge of the incoming pulses. The relationship
of the states of these two inputs determines the direction of the count. See
T
able 1-1. T
ypical devices for counting are high-speed static switches or
incremental encoders.
T
able 1-1
Deter
mining Count in Pulse Counter Mode
Counter
Direction Edge A
Input
B Input
up
up
down
down
”
”
#
#
low
high
high
low
In
the pulse counter mode, the channel senses the edges
of the A or the B
input to count up or down. See Figure 1-4. T
o reliably record this transition
from low to high, the pulse width must be at least 8
s.
Count Value
Count Input
2 3 2 1
8s
min
Input A
Input B
Count Up
Count Down
Pulse Counter Mode
11 s
min
1
Figure 1-4
Pulse
Counter Mode 0