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GD32F20x User Manual
331
ITI0/1/2/3. This mode can be selected by setting SMC [2:0] to 0x7 and the TRGS [2:0] to 0x0,
0x1, 0x2 or 0x3.
SMC1== 1’b1 (
external clock mode 1
). External input is selected as timer clock source
(ETI)
The TIMER_CK, which drives 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 to 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 ETI signal is
selected as clock source, the trigger controller including the edge detection circuitry will
generate a clock pulse on each rising edge of ETI signal to provide clock to the counter
prescaler.
Prescaler
The prescaler can divide the timer clock (TIMER_CK) to a counter clock (PSC_CLK) by any
factor between 1 and 65536. It is controlled by prescaler register (TIMERx_PSC) which can
be changed on the go but is taken into account at the next update event.
Figure 18-3. Counter timing diagram with prescaler division change from 1 to 2 (PSC
value change from 0 to 1)
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
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 ...
Страница 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Страница 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
Страница 385: ...GD32F20x User Manual 385 ...
Страница 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...