Advanced-control timers (TIM1/TIM8/TIM20) RM0440
1152/2126 RM0440 Rev 4
Commercially available encoders are proposed with several options for index pulse
conditioning, as per the Figure 335 below:
• gated with A and B: the pulsewidth is 1/4 of one channel period, aligned with both A
and B edges
• gated with A (or gated with B): the pulsewidth is 1/2 of one channel period, aligned with
the two edges on channel A (resp. channel B)
• ungated: the pulsewidth is up to one channel period, without any alignment to the
edges
Figure 335. Index gating options
The circuitry tolerates jitter on index signal, whatever the gating mode, as show on
Figure 336 below.
In ungated mode, the signal must be strictly below 2 encoder periods. If the pulsewidth is
greater or equal to 2 encoder period, the counter will be reset multiple times.
Figure 336. Jittered Index signals
The timer supports the 3 gating options identically, without any specific programming
needed. It is only necessary to define on which encoder state (i.e. channel A and channel B
MSv45765V1
Gated A & B
Gated A
Ungated
Channel B
Channel A
MSv45766V1
Gated A & B
Gated A
Ungated
Channel B
Channel A
Max pulsewidth ungated mode
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