Lenze EPM-T110 - Measuring the Period (Mode 4)

Parameterising 1xcounter/16xdigital input module
Measuring the period (mode 4)
12
Parameter setting
12.6
12.6.7
l
12.6-13
EDSPM-TXXX-3.0-04/2004
12.6.7 Measuring the period (mode 4)
In mode 4 the counter operates as a permanent period meter. The counter counts
the number of rising edges of a reference counter between two rising edges of
signal A (E.0).
The frequency of a reference counter can be preset in the Rx PDO in byte 5 (Ref.
Freq.).
Byte Assignment
5 Reference frequency
00
h
16 MHz
5
R
e
f
e
r
e
n
c
e
f
r
e
q
u
e
n
c
y
01
h
8MHz
02
h
4MHz
03
h
1MHz
04
h
100 kHz
05
h
10 kHz
06
h
1kHz
07
h
100 Hz
08
h...
FF
h
not permissible
The software gate which releases the counting process, is opened when bit 0
(Start) in the byte 4 (Control)has HIGH level. It is closed as soon as bit 1 (Stop)has
HIGH level.
When the software gate is open:
z The reference counter is started by the first rising edge of signal A and then
incremented with every rising edge of the reference clock.
z The next rising edge of signal A stops the reference counter.
The counter can be cleared at any time via a HIGH level in byte 4 (Control), bit 3
(Clear). Then the measuring process is restarted with the next rising edge of signal
A.
1
T Period
T =
1
f
⋅ n
f
ref
Reference frequency
T
f
ref
n
n Count value
Example: Reference frequency f
ref
= 1 MHz, count value n = 10,000
T =
1
1MHz
⋅ 10000 = 10 ms


 Note!
The count value remains valid until the next measurement is
completed or the counter is reset via the clear signal; this means
that you do not get the current count value but the one from the
previous measurement if a measurement has not been completed,
e.g. because no second rising edge of signal A has occurred.
Reference frequency
Start/ stop signal
Asignal
Clear signal
Period calculation
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