36 Process Image
WAGO-I/O-SYSTEM 750 XTR
750-404/040-003 Counter Adjust XTR
Manual
Version 1.1.0
4
Process Image
Mapping of process data in the process image of fieldbus systems
The representation of the process data of some I/O modules or their variants in
the process image depends on the fieldbus coupler/controller used. Please take
this information from the section “I/O Modules” included in the description
concerning the process image of the corresponding coupler/controller.
4.1
Frequency Measurement
In operating mode “Frequency Counter,” the 750-404/040-003 I/O module
records the time between one or several rising edges of the “CLOCK” input signal
and calculates the signal frequency.
The process image is calculated and updated at every first, fourth or sixteenth
rising edge. This depends on the integration time set in the control byte.
When a rising edge is first detected, the cyclical periodic measurement starts. At
this point, no valid frequency value can be delivered yet. In this case, the counter
module transmits 0xFFFFFFFF as input information. If a statistical high or low
signal is present at the “CLOCK” input, the same input value is returned.
If there is no signal change at the “CLOCK” input, the counter module can also
update the process image after defined, parameterizable time intervals
(watchdog time). In this case, the counter module also transmits the invalid value
0xFFFFFFFF.
Figure 7: Time Diagram: Process Data Update Sequence (integration time = 1 period)