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Rev. 1.00
368 of 576
January 28, 2022
32-Bit Arm
®
Cortex
®
-M0+ MCU
HT32F54231/HT32F54241/HT32F54243/HT32F54253
16 Single-Channel T
imer (SCTM)
Clock Controller
The following describes the Timer Module clock controller which determines the clock source of
the internal prescaler counter.
▆
Internal APB clock f
CLKIN
The default internal clock source is the APB clock f
CLKIN
used to drive the counter prescaler when
the slave mode is disabled. When the slave mode selection bits SMSEL are set to 0x4, 0x5 or
0x6, the internal APB clock f
CLKIN
is the counter prescaler driving clock source. If the slave mode
controller is enabled by setting SMSEL field in the MDCFR register to 0x7, the prescaler is
clocked by other clock sources selected by the TRSEL field in the TRCFR register and described
as follows.
▆
STIED
The counter prescaler can count during each rising edge of the STI signal. This mode can be
selected by setting the SMSEL field to 0x7 in the MDCFR register. Here the counter will act
as an event counter. The input event, known as STI here, can be selected by setting the TRSEL
field to an available value except the value of 0x0. When the STI signal is selected as the clock
source, the internal edge detection circuitry will generate a clock pulse during each STI signal
rising edge to drive the counter prescaler. It is important to note that if the TRSEL field is set to
0x0 to select the software UEVG bit as the trigger source, then when the SMSEL field is set to
0x7, the counter will be updated instead of counting.
PSCR
CRR
CNTR
Reset
CLK
PSC Prescaler
Reset
CLK
TM_CNT
f
CLKIN
(Internal APB clock)
TRSEL
SMSEL
Overflow
CK_PSC
CK_CNT
UEVG bit
Slave Restart
mode trigger
Update Event
Start/Stop
STIED
(Trigger events)
Figure 118. SCTM Clock Source Selection