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3. PWM
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20.3.2.1 Input Pin Logic
Each Compare/Capture channel can be configured as an input source for the Capture Unit or as external
clock source for the Timer (see Figure 20.10 (p. 526) ). Compare/Capture channels 0 and 1 are the
inputs for the Quadrature Decoder Mode. The input channel can be filtered before it is used, which
requires the input to remain stable for 5 cycles in a row before the input is propagated to the output.
Figure 20.10. TIMER Input Pin Logic
INSEL
TIMn _CCx
PRS channels
PRSSEL
Filt er
FILT
ICEDGE
Input
Capt ure x
20.3.2.2 Compare/Capture Registers
The Compare/Capture channel registers are prefixed with TIMERn_CCx_, where the x stands for the
channel number. Since the Compare/Capture channels serve three functions (input capture, compare,
PWM), the behavior of the Compare/Capture registers (TIMERn_CCx_CCV) and buffer registers
(TIMERn_CCx_CCVB) change depending on the mode the channel is set in.
20.3.2.2.1 Input Capture mode
When running in Input Capture mode, TIMERn_CCx_CCV and TIMERn_CCx_CCVB form a FIFO buffer,
and new capture values are added on a capture event, see Figure 20.11 (p. 526) . The first capture
can always be read from TIMERn_CCx_CCV, and reading this address will load the next capture value
into TIMERn_CCx_CCV from TIMERn_CCx_CCVB if it contains valid data. The CC value can be read
without altering the FIFO contents by reading TIMERn_CCx_CCVP. TIMERn_CCx_CCVB can also be
read without altering the FIFO contents. The ICV flag in TIMERn_STATUS indicates if there is a valid
unread capture in TIMERn_CCx_CCV.
In case a capture is triggered while both CCV and CCVB contain unread capture values, the buffer
overflow interrupt flag (ICBOF in TIMERn_IF) will be set. New capture values will on overflow overwrite
the value in TIMERn_CCx_CCVB.
Note
In input capture mode, the timer will only trigger interrupts when it is running
Figure 20.11. TIMER Input Capture Buffer Functionality
CN T
CCV B
CCV
FIFO
20.3.2.2.2 Compare and PWM Mode
When running in Output Compare or PWM mode, the value in TIMERn_CCx_CCV will be compared
against the count value. In Compare mode the output can be configured to toggle, clear or set
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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