Operating Mode Impulse Width And Period Width Measurement - Jäger ADwin-Gold-USB Manual

ADwin
8.4 Operating Mode Impulse Width and Period Width
Measurement
In this operating mode an internal reference clock generator clocks the counter
with a signal frequency of 20 MHz or (after a prescaler) 5 MHz. All counters
have a switch in order to change the signal frequency. The period duration or
pulse width of a square-wave signal at input CLR/LATCH can be measured.
In this mode you have to consider at high frequencies that your GLOBALDELAY
remains smaller than a signal period, in order to acquire a cycle.
8.4.1 Period Duration Measurement
All four counters can execute period duration measurements.
LATCH 4k7
ref.-CLK
G
20 MHz
to f
ref
other counters
Fig. 23 – Block diagram of the CO1 add-on in the mode
"period duration measurement"
In this mode, the counter values are latched into Latch A at every positive edge,
and the previous data are overwritten. The pulse width will be derived from the
counter value difference multiplied by the period duration of the reference clock.
INIT:
. . .
CNT_ENABLE(0)
CNT_CLEAR(1)
CNT_MODE(1)
CNT_SET(0)
CNT_SET(1)
CNT_INPUTMODE(1)
CNT_SE_DIFF(0)
CNT_ENABLE(1)
EVENT:
CNT_READLATCH(1)
. . .
ADwin-Gold USB / ENET, manual version 3.8, October 2005
32 bit Latch A
f
ref
switch
Divider
CLK
÷ 4
Up
DIR
32 bit Counter
CLR
EN
switches of
Control Registers
initialization ...
disable counters
clear counter(s)
mode "internal reference clock" with ...
... 20 MHz or
... 5 MHz reference frequency
input CLR/LATCH as LATCH input
select single-ended inputs
enable counter(s)
event loop ...
read out latch A
evaluate counter value in process
CO1 Counter Add-On
Reference clock
generator
Data
Data
Programming example
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