HIMax System 3 Product Description
HI 801 001 E Rev. 4.01 Page 39 of 122
3.5.3 Noise Blanking Sequence
The examples illustrate the sequence of noise blanking:
A transient interference is blanked out.
An existing interference - longer than the maximum noise blanking time - triggers the
safe reaction.
Example 1: Transient Interference is Successfully Blanked Out
Cycle, Duration = Watchdog Time
Read-in Process in 1
st
Cycle
Read-in Process 2
st
Cycle
Read-in Process 3
rd
Cycle
Read-in Process in 4
th
Cycle
Processing (in all Cycles)
Output Process in 1
st
and 2
nd
Cycle
Output Process in 3
rd
Cycle
Output Process in 4
th
Cycle
Safety Time Duration
Figure 9: Transient Interference
In example 1, valid input values are read within one cycle at
. For this cycle, the system
processes the valid input values, even though an interference occurred directly upon
completion of the read-in process.
If the interference is still present in the following cycle during the read-in process
, the
module detects the interference and the system decides if noise blanking can be performed
at this point in time based on the following rule:
Safety time - elapsed time - (2 * watchdog time) > 0
Elapsed time = Time interval between the moment, in which the last valid values were read
in, and the moment, in which the interference was detected.
Noise blanking is possible since the interference is present for less than a cycle ( = elapsed
time) and two additional cycles (2 * watchdog time) are available for triggering a safe
reaction. For this cycle, the system processes the last valid input values of
and no
defined fault reactions are triggered. The transient interference was successfully blanked
out.
If the interference is no longer present in
, new valid values are read in and processed.
If noise blanking is not active, the system immediately triggers the defined fault reactions
during the read-in process
.
To Next Page
Loading...
Need help?
General
