STM8AF6388 Product overview
The ROP circuit may provide a temporary access for debugging or failure analysis. The temporary read access is protected by a user defined, 8-byte keyword stored in the option byte area. This keyword must be entered via the SWIM interface to temporarily unlock the device.
If desired, the temporary unlock mechanism can be permanently disabled by the user through OPT6/NOPT6 option bytes.
5.5.1 Features
• Clock sources
– 16 MHz high-speed internal RC oscillator (HSI)
– 128 kHz low-speed internal RC (LSI)
– 1-24 MHz high-speed external crystal (HSE)
– Up to 24 MHz high-speed user-external clock (HSE user-ext)
• Reset : After reset the microcontroller restarts by default with an internal 2-MHz clock
(16 MHz/8). The clock source and speed can be changed by the application program as soon as the code execution starts.
• Safe clock switching : Clock sources can be changed safely on the fly in Run mode through a configuration register. The clock signal is not switched until the new clock source is ready. The design guarantees glitch-free switching.
• Clock management : To reduce power consumption, the clock controller can stop the clock to the core, individual peripherals or memory.
• Wakeup : In case the device wakes up from low-power modes, the internal RC oscillator (16 MHz/8) is used for quick startup. After a stabilization time, the device switches to the clock source that was selected before Halt mode was entered.
• Clock security system (CSS) : The CSS permits monitoring of external clock sources and automatic switching to the internal RC (16 MHz/8) in case of a clock failure.
• Configurable main clock output (CCO) : This feature permits to output a clock signal for use by the application.
5.5.2
The clock controller distributes the system clock coming from different oscillators to the core and the peripherals. It also manages clock gating for low-power modes and ensures clock robustness.
16 MHz high-speed internal RC oscillator (HSI)
• Default clock after reset 2 MHz (16 MHz/8)
• Fast wakeup time
User trimming
The register CLK_HSITRIMR with two trimming bits plus one additional bit for the sign permits frequency tuning by the application program. The adjustment range covers all possible frequency variations versus supply voltage and temperature. This trimming does not change the initial production setting.
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