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...the world's most energy friendly microcontrollers
2012-04-24 - Giant Gecko Family - d0053_Rev0.96 526
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3. PWM
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
TIMn_CCx
PRS channels
PRSSEL
INSEL
Filter
FILT
ICEDGE
Input
Capture 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
FIFO
CNT
CCV
CCVB
APB Data
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