STM32L4复位和时钟控制(RCC)介绍

• MSI by default
Clocks: PLL
• 3 PLLs
• Each with 3 independent outputs • PLLs input frequency must be between 4 and 16 MHz • PLL input can be MSI/HSI or HSE f(VCO clock) = (f(PLL clock input)/PLLM) × PLLN f(PLL_P) = f(VCO clock) / PLLP f(PLL_Q) = f(VCO clock) / PLLQ f(PLL_R) = f(VCO clock) / PLLR PLLM from 1 to 8 PLLN from 8 to 86 PLLP = 7 or 17 PLLQ = 2, 4, 6, 8 PLLR = 2, 4, 6, 8
100 kHz, 200 kHz, 400 kHz, 800 kHz, 1 MHz, 2 MHz, 4 MHz (reset value), 8 MHz, 16 MHz, 24 MHz, 32 MHz, 48 MHz.
89
• After Reset and Shutdown, MSI frequency is 4 MHz, selected by MSISRANGE in RCC_CSR register • After Standby: Frequency selected from 1, 2, 4 or 8 MHz with MSISRANGE in RCC_CSR register. • MSIRGSEL must be set in RCC_CR to switch to the frequency selected by MSIRANGE
98
• Clock-out capability :
• MCO selected between :
• LSI • LSE • SYSCLK • • • HSI HSE PLLCLK • MSI
• LSCO selected between :
• LSI • LSE
Available in all modes except VBAT
• • • • • • • • Low level on the NRST pin (External Reset) WWDG event IWDG event Firewall event A software reset (through NVIC) Low-power mode security reset Option byte loader reset Brown-out Reset
87
• Backup domain RESET
• Resets in the Backup domain: RTC registers + Backup Registers + RCC BDCR register • Sources
• BDRST bit in RCC BDCR register • VDD or VBAT power on, if both supplies have previously been powered off
• Reset flag source can be found in RCC_CSR register
RESET Sources
• Power RESET
• Sources
• Brown-out reset BOR => reset all registers except those in Backup domain • Exit from STANDBY => all registers in VCORE domain are reset Registers outside the VCORE domain (RTC, WKUP, IWDG, and Standby/Shutdown modes control) are not impacted. • Exit from SHUTDOWN generates a BOR Reset.
• LSI 32kHz
Parameters Accuracy over parts Accuracy over temperature STM32L15x 26..56KHz -10% / +4% (0..85°C) 400nA STM32L4x ~8% 2% (-40 125°C) 110nA
9ET PULSE GENERATOR (min 20µs) IWDG RESET Firewall RESET Option byte loading RESET Software RESET BOR RESET Low power management RESET
92
Clocks: HSE(High-Speed External)
• HSE 4-48MHz
• External source (Bypass mode) up to 40 MHz • External Crystal/Ceramic resonator (4-48MHz)
93
• Clock Security System (CSS)
Clocks
• Peripheral clocks Enable registers:
RCC_AHBxENR, RCC_APBxENRy:
• Peripheral clock disable by default (except Flash) • After enable bit is set: 2 clock cycles delay before clock to be active • Registers read and write access not supported when clock is disable. • Caution: SRAM1 and SRAM2 do not have enable bit
91
HSI vs. MSI (design spec)
MSI Normal mode Over temperature: ±6% Accuracy (max) Over voltage: From 100 to 800 kHz : ±1% From 1 to 8 MHz : ±2% From 16 to 48 MHz : ±4% 100 kHz : 0.5 µA 800 kHz : 2µA Consumption (typ) 1 MHz : 5µA 8 MHz : 20 µA 16 MHz : 60 µA 48 MHz : 160 µA Startup time (typ) 100 kHz : 10 µs 48 MHz : 2.5 µs 1.25 ms for 5% of final freq. 0.9 µs 130 µA Better than 0.25% TBD PLL-mode HSI
Clocks: MSI (Multi-Speed Internal)
• MSI = clock at startup from Reset, Standby or Shutdown modes. • Programmable frequency : 12 ranges selected with MSIRANGE in RCC_CR:
Reset and clock control (RCC)
RESET Sources
86
• System RESET
• Resets all registers except some RCC registers, PWR registers and Backup domain • Sources
02/07/2015 PLLP from 2 to 31 in derivatives
94
5,6,7,8
System clock
• Selected between HSI/HSE/MSI/PLL • Maximum frequency 80 MHz • APB1 and APB2 up to 80 MHz • Clock source max frequency depending on voltage scaling:
Clocks: MSI (Multi-Speed Internal)
• Can be selected as clock at wakeup from Stop 1 or 2 modes / CSS backup clock • Normal mode and PLL-mode (=auto-calibration with LSE) PLL-mode : allows USB FS device functionality (0.25% accuracy) • Factory and user trimmed
Crystal (max)
Consumption (typ) 200 nA 260 nA 410 nA 540 nA
50kOhm/6pF 80kOhm/6pF 50kOhm/12.5pF 80kOhm/12.5pF
• Available in all low-power modes + VBAT
Clocks: LSI (Low-Speed Internal)
95
Clocks: LSE (Low-Speed External)
• LSE: programmable amplifier driving capability (4 modes)
96
Mode Ultra low power Medium low driving Medium high driving High driving
Consumption (typ)
• Available in all low-power modes except Shutdown and VBAT