RM0440 Rev 4 1291/2126
RM0440 General-purpose timers (TIM2/TIM3/TIM4/TIM5)
1343
In down-counting mode, the detection is conditioned by a preliminary transition from 1 to 0.
This is to cope with narrow index pulses in gated A and B mode, as shown on Figure 426
below, to avoid any false error detection in case the encoder dithers between TIMx_ARR
and 0 immediately after the index detection.
Figure 426. Down-counting encode error detection
An index error sets the IERRF interrupt flag in the TIMx_SR status register. An index error
interrupt will be generated if the IERRIE bit is set in the TIMx_DIER register.
Functional encoder Interrupts
The following interrupts are also available in encoder mode
• Direction change: any change of the counting direction in encoder mode will cause the
DIR bit in the TIMx_CR1 register to toggle. The direction change sets the DIRF
interrupt flag in the TIMx_SR status register. A direction change interrupt will be
generated if the DIRIE bit is set in the TIMx_DIER register.
• Index event: the Index event sets the IDXF interrupt flag in the TIMx_SR status register.
An Index interrupt will be generated if the IDXIE bit is set in the TIMx_DIER register.
MSv47416V1
Channel A
Channel B
IERRF
Index
Channel A
Channel B
IERRF
Counter
2 1 0 7 0
5
Counter 2 1 0 7 6
4
5
Error detected Error asserted
No error: transition from 0 to
TIMx_ARR following an index
No error: transition from 0 to
TIMx_ARR without index, but not
following a transition from 1 to 0
7 6
Index
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