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GD32F20x User Manual
389
SMC1== 1’b1 (external clock mode 1). External input pin source (ETI)
The TIMER_CK, driven counter’s prescaler to count, can be triggered by the event of rising
or falling edge on the external pin ETI. This mode can be selected by setting the SMC1 bit in
the TIMERx_SMCFG register to 1. The other way to select the ETI signal as the clock source
is set the SMC [2:0] to 0x7 and the TRGS [2:0] to 0x7 respectively. Note that the ETI signal
is derived from the ETI pin sampled by a digital filter. When the clock source is selected to
come from the ETI signal, the trigger controller including the edge detection circuitry will
generate a clock pulse during each ETI signal rising edge to clock the counter prescaler.
Prescaler
The prescaler can divide the timer clock (TIMER_CK) to the counter clock (PSC_CLK by any
factor between 1 and 65536. It is controlled through prescaler register (TIMERx_PSC) which
can be changed on the go but be taken into account at the next update event.
Figure 18-34. Counter timing diagram with prescaler division change from 1 to 2
TIMER_CK
CEN
PSC_CLK
CNT_REG
Reload Pulse
Prescaler CNT
Prescaler BUF
F7
F8
F9
FA FB
FC
01
02
03
0
1
0
1
0
1
0
1
0
1
0
1
PSC value
0
04
UPG
0
Up counting mode
In this mode, the counter counts up continuously from 0 to the counter-reload value, which is
defined in the TIMERx_CAR register, in a count-up direction. Once the counter reaches the
counter reload value, the counter restarts to count once again from 0. The update event is
generated at each counter overflow. The counting direction bit DIR in the TIMERx_CTL1
register should be set to 0 for the up counting mode.
When the update event is set by the UPG bit in the TIMERx_SWEVG register, the counter
value will be initialized to 0 and generates an update event.
Содержание GD32F20 Series
Страница 1: ...GigaDevice Semiconductor Inc GD32F20x ARM Cortex M3 32 bit MCU User Manual Revision 2 2 Oct 2019 ...
Страница 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
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Страница 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
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Страница 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...