LTDVE8CH-20 – INSTRUCTION MANUAL
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TR8), while the eight light outputs (LD1, LD2, LD3, LD4, LD5, LD6, LD7 and LD8) and the eight
synchronization outputs (SH1, SH2, SH3, SH4, SH5, SH6, SH7 and SH8) are drawn at the right.
A description of each of the blocks is given in the next sections.
12.2. Input filters
The input filters are used to debounce and remove glitches from the incoming synchronization inputs.
Each of the eight synchronization inputs has a dedicated, independent filter.
The algorithm implemented in each of the filters processes the relevant synchronization input with a
finite state machine. A change in the filter output is performed only when the input signal has
remained constant for a defined period of time, called filter time constant. Any pulses shorter than the
filter time constant are thus removed and not passed through.
The diagram in
Figure 5: operation of the input filter
shows the filter operation on a random input
signal.
Figure 5: operation of the input filter
As visible, the input signal is filtered by looking for pulses that hold the same state for a time of at
least
Tfilter
before the change in state is passed to the output. Please note there is a fixed input to
output propagation delay equal to this filter time constant.
Each of the four filters can be set as follows:
•
No filtering (pass through)
•
Filtering with a 10µs time constant
•
Filtering with a 20µs time constant
•
Filtering with a 50µs time constant
•
Filtering with a 100µs time constant
•
Filtering with a 200µs time constant
•
Filtering with a 500µs time constant
Setting of the filters can be done using the serial RS485 or Ethernet interfaces.
12.3. Input multiplexers
The input multiplexers are used to send the filtered inputs to the pulse generators. There are sixteen
input multiplexers organized in a 9x16 routing matrix.
input
Tfilter
output
Tfilter
Tfilter
Tfilter
