ST7FOXF1 Datasheet, PDF (36/226 Pages) STMicroelectronics – 8-bit MCU with single voltage Flash memory, SPI, I²C, ADC, timers

Supply, reset and clock management
ST7FOXF1, ST7FOXK1, ST7FOXK2
Caution:
If a programming cycle is interrupted (by a RESET action), the integrity of the data in
memory will not be guaranteed.
When the Read-Out Protection is enabled through an option bit (see Section 13.1: Option
bytes), these two bytes are protected against Read-out (including a re-write protection). In
Flash devices, when this protection is removed by reprogramming the option byte, these two
bytes are automatically erased.
Figure 10. RC user calibration programming cycle
Internal
Programming
voltage
READ OPERATION NOT POSSIBLE
READ OPERATION POSSIBLE
WRITE OF ^{ERASE CYCLE}
WRITE CYCLE
DATA LATCHES
t_PROG
Byte 1 Byte 2
RCCLAT
RCCPGM
t_PROG is typically 5 ms and max 10 ms
6.1.3
Auto wakeup RC oscillator
The ST7FOX also contains an Auto wakeup RC oscillator. This RC oscillator should be
enabled to enter Auto wakeup from halt mode.
The Auto wakeup (AWU) RC oscillator can also be configured as the startup clock through
the CKSEL[1:0] option bits (see Section 13.1: Option bytes on page 211).
This is recommended for applications where very low power consumption is required.
Switching from one startup clock to another can be done in run mode as follows (see
Figure 11):
Case 1 Switching from internal RC to AWU
1. Set the RC/AWU bit in the CKCNTCSR register to enable the AWU RC oscillator
2. The RC_FLAG is cleared and the clock output is at 1.
3. Wait 3 AWU RC cycles till the AWU_FLAG is set
4. The switch to the AWU clock is made at the positive edge of the AWU clock signal
5. Once the switch is made, the internal RC is stopped
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