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GD32E23x User Manual
266
Reserved
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
ETP
SMC1
ETPSC[1:0]
ETFC[3:0]
MSM
TRGS[2:0]
OCRC
SMC[2:0]
rw
rw
rw
rw
rw
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Bits
Fields
Descriptions
31:16
Reserved
Must be kept at reset value
15
ETP
External trigger polarity
This bit specifies the polarity of ETI signal
0: ETI is active at rising edge or high level .
1: ETI is active at falling edge or low level .
14
SMC1
Part of SMC for enable External clock mode1
In external clock mode 1, the counter is clocked by any active edge on the ETIF
signal.
0: External clock mode 1 disabled
1: External clock mode 1 enabled.
When the slave mode is configured as restart mode, pause mode or event mode,
the timer can still work in the external clock 1 mode by setting this bit. But the
TRGS bits must not be 3’b111 in this case.
The clock source of the timer will be ETIFP if external clock mode 0 and external
clock mode 1 are configured at the same time.
Note:
External clock mode 0 enable is in this register’s SMC[2:0] bit-filed.
13:12
ETPSC[1:0]
The prescaler of external trigger
The frequency of external trigger signal ETIFP must not be at higher than 1/4 of
TIMER_CK frequency. When the external trigger signal is a fast clock, the
prescaler can be enabled to reduce ETIFP frequency.
00: Prescaler disable.
01: The prescaler is 2.
10: The prescaler is 4.
11: The prescaler is 8.
11:8
ETFC[3:0]
External trigger filter control
The external trigger can be filtered by digital filter and this bit-field configure the
filtering capability.
Basic principle of digital filter: continuously sample the external trigger signal
according to f
SAMP
and record the number of times of the same level of the signal.
After reaching the filtering capacity configured by this bit-field, it is considered to be
an effective level.
The filtering capability configuration is as follows:
EXTFC[3:0]
Times
f
SAMP
4’b0000
Filter disabled.
4’b0001
2
f
CK_TIMER