MINI57TDE Datasheet, PDF (89/131 Pages) List of Unclassifed Manufacturers – 32-bit Microcontroller

Mini57
6.3.2 Auto Trim
This chip supports auto-trim function: the HIRC trim (48 MHz RC oscillator), according to the accurate
LXT (32.768 kHz crystal oscillator), automatically gets accurate HIRC output frequency, 0.25 %
deviation within all temperature ranges.
For instance, the system needs an accurate 48MHz clock. In such case, if users do not want to use
PLL as the system clock source, they need to solder 32.768 kHz crystal in system, and set FREQSEL
(SYS_IRCTCTL[0] trim frequency selection) to “1”, and the auto-trim function will be enabled. Interrupt
status bit FREQLOCK (SYS_IRCTISTS[0] HIRC frequency lock status) “1” indicates the HIRC output
frequency is accurate within 0.25% deviation. To get better results, it is recommended to set both
LOOPSEL (SYS_IRCTCTL[5:4] trim calculation loop) and RETRYCNT (SYS_IRCTCTL[7:6] trim value
update limitation count) to “11”.
6.3.3 System Clock and SysTick Clock
The system clock has three clock sources which were generated from clock generator block. The
clock source switch depends on the register HCLKSEL (CLK_CLKSEL0[1:0]). The block diagram is
shown in Figure 6.3-3.
HCLKSEL (CLK_CLKSEL0[1:0])
48 MHz HIRC
11
10 kHz LXT
01
4~24 MHz HXT or
32.768 kHz LXT
00
1/(HCLKDIV+1)
HCLKDIV (CLK_CLKDIV[3:0])
CPUCLK
HCLK
PCLK
CPU
AHB
APB
CPU in Power Down Mode
Legend:
HXT = 4~24 MHz external high speed crystal oscillator
HIRC = 48 MHz internal high speed RC oscillator
LIRC = 10 kHz internal low speed RC oscillator
Figure 6.3-3 System Clock Block Diagram
The clock source of SysTick in the Cortex^® -M0 core can use CPU clock or external clock
CLKSRC(SYST_CTL[2]). If using external clock, the SysTick clock (STCLK) has 4 clock sources.
The clock source switch depends on the setting of the register STCLKSEL (CLK_CLKSEL0[4:3]).
The block diagram is shown in Figure 6.3-4.
Apr. 06, 2017
Page 89 of 131
Rev.1.00