STM8AFSLASHP6348 datasheet(17/95 Pages) STMICROELECTRONICS

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DS12343 Rev 2

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STM8AF6366

Product overview

5.4.4

Read-out protection (ROP)

The STM8A provides a read-out protection of the code and data memory which can be

activated by an option byte setting (see the ROP option byte in section 10).

The read-out protection prevents reading and writing Flash program memory, data memory

and option bytes via the debug module and SWIM interface. This protection is active in all

device operation modes. Any attempt to remove the protection by overwriting the ROP

option byte triggers a global erase of the program and data memory.

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

bytes 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

Clock controller

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.

5.5.1

Features

•

Clock sources

–

16 MHz high-speed internal RC oscillator (HSI)

–

128 kHz low-speed internal RC (LSI)

–

1-16 MHz high-speed external crystal (HSE)

–

Up to 16 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 or individual peripherals.

•

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.

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