General-purpose timers (TIM2/TIM3/TIM4)
RM0365
599/1080
DocID025202 Rev 7
21.4.3
TIMx slave mode control register (TIMx_SMCR)
Address offset: 0x08
Reset value: 0x0000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
SMS[3]
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15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
ETP
ECE
ETPS[1:0]
ETF[3:0]
MSM
TS[2:0]
OCCS
SMS[2:0]
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Bits 31:17 Reserved, must be kept at reset value.
Bit 16
SMS[3]
:
Slave mode selection - bit 3
Refer to SMS description - bits 2:0
Bit 15
ETP
: External trigger polarity
This bit selects whether ETR or ETR is used for trigger operations
0: ETR is non-inverted, active at high level or rising edge
1: ETR is inverted, active at low level or falling edge
Bit 14
ECE
: External clock enable
This bit enables External clock mode 2.
0: External clock mode 2 disabled
1: External clock mode 2 enabled. The counter is clocked by any active edge on the ETRF
signal.
1
:
Setting the ECE bit has the same effect as selecting external clock mode 1 with TRGI
connected to ETRF (SMS=111 and TS=111).
2
:
It is possible to simultaneously use external clock mode 2 with the following slave modes:
reset mode, gated mode and trigger mode. Nevertheless, TRGI must not be connected to
ETRF in this case (TS bits must not be 111).
3
:
If external clock mode 1 and external clock mode 2 are enabled at the same time, the
external clock input is ETRF.
Bits 13:12
ETPS[1:0]
: External trigger prescaler
External trigger signal ETRP frequency must be at most 1/4 of CK_INT frequency. A
prescaler can be enabled to reduce ETRP frequency. It is useful when inputting fast external
clocks.
00: Prescaler OFF
01: ETRP frequency divided by 2
10: ETRP frequency divided by 4
11: ETRP frequency divided by 8