GD32W51x User Manual
470
Mode Selection
Source Selection
Polarity Selection
Filter and Prescaler
Exam 3
Event m ode
The counter w ill start
to count w hen 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 17-26. Event m ode
TIMER_CK
CNT_REG
5E
5F
60
61
ETI
TRGIF
ETIFP
Single pulse mode
Single pulse mode is opposite to the repetitive mode, which can be enabled by setting SPM
in TIMERx_CTL0. When you set SPM, the counter will be clear and stop when the next update
event automatically. In order to get pulse waveform, you can set the TIMERx to PWM mode
or compare by CHxCOMCTL.
Once the timer is set to operate in the single pulse mode, it is not necessary to set the timer
enable bit CEN in the TIMERx_CTL0 register to 1 to enable the counter. The trigger to
generate a pulse can be sourced from the trigger signals edge or by setting the CEN bit to 1
using software. Setting the CEN bit to 1 or a trigger from the trigger signals 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 using software, the counter will be
stopped and its value 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 trigger active edge which sets the CEN bit to 1 will enable the
counter. However, there exist 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 each 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 operate in the PWM0 or PWM1 output mode and
the trigger source is derived from the trigger signal.