GD32F403xx User Manual
327
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]
Reserved
SMC[2:0]
rw
rw
rw
rw
rw
rw
rw
Bits
Fields
Descriptions
15
ETP
External trigger polarity
This bit specifies the polarity of ETI signal
0: ETI is active at high level or rising edge.
1: ETI is active at low level or falling edge.
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.
It is possible to simultaneously use external clock mode 1 with the restart mode,
pause mode or event mode. But the TRGS bits must not be 3’b111 in this case.
The external clock input will be ETIF if external clock mode 0 and external clock
mode 1 are enabled at the same time.
Note
: External clock mode 0 enable is in this register’s SMC bit-filed.
13:12
ETPSC[1:0]
External trigger prescaler
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
4’b0010
4
4’b0011
8
4’b0100
6
f
DTS_CK
/2
4’b0101
8