GD32VF103 User Manual
247
Mode Selection
Source Selection
Polarity Selection
Filter and Prescaler
Exam3
Event mode
The counter will start
to count when a
rising edge of trigger
input comes.
TRGS[2:0] =3’b111
ETIFP is selected.
ETP = 0, the polarity
of ETI does not
change.
ETPSC = 1, ETI is
divided by 2.
ETFC = 0, ETI does not
filter.
Figure 15-26. Event mode
TIMER_CK
CNT_REG
5E
5F
60
61
ETI
TRGIF
ETIFP
Single pulse mode
Single pulse mode is enabled by setting SPM in TIMERx_CTL0. If SPM is set, the counter
will be cleared and stopped automatically when the next update event occurs. In order to get
a pulse waveform, the TIMERx is configured to PWM mode or compare mode by
CHxCOMCTL.
Once the timer is set to the single pulse mode, it is not necessary to configure the timer enable
bit CEN in the TIMERx_CTL0 register to 1 to enable the counter. Setting the CEN bit to 1 or
a trigger signal edge can generate a pulse and then keep the CEN bit at a high state until the
update event occurs or the CEN bit is written to 0 by software. If the CEN bit is cleared to 0
by software, the counter will be stopped and its value will be held. If the CEN bit is
automatically cleared to 0 by a hardware update event, the counter will be reinitialized.
In the single pulse mode, the active edge of trigger which sets the CEN bit to 1 will enable the
counter. However, there exists several clock delays to perform the comparison result between
the counter value and the TIMERx_CHxCV value. In order to reduce the delay to a minimum
value, the user can set the CHxCOMFEN bit in TIMERx_CHCTL0/1 register. After a trigger
rising occurs in the single pulse mode, the OxCPRE signal will immediately be forced to the
state which the OxCPRE signal will change to, as the compare match event occurs without
taking the comparison result into account. The CHxCOMFEN bit is available only when the
output channel is configured to the PWM mode 0 or PWM mode 1 and the trigger source is
derived from the trigger signal.