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CMS80F731x Reference Manual
3.6
CONFIG Status Protection Reset
CONFIG state protection reset is an enhanced protection mechanism of the system. During power-on reset, there is an
internal set of 16-bit CONFIG registers that load the fixed code set in flash (A569H) and do not operate during normal operation.
If, in the case of a particular non-program operation, the value of the register changes and is not equal to the original fixed code,
and after several clock samples, the register continues to remain in a state that is not fixed code, the system will reset.
This reset mechanism prevents changes in configuration bits under certain conditions, so that the system enters an
unpredicted state.
In normal operation, the clock of the sample register value is the internal RC fixed clock Fixed_Clock (8MHz, clock source
from HSI) and low power clock (LSI 125KHz), once the value of the register is not a fixed code, force the LSI oscillator and HSI
oscillator to be enabled, and the system clock switches to the LSI clock, if after 12 Fixed_Clock sampling or 3 LSI clock sampling,
the register remains not in a fixed code state, The system generates a reset.
Under certain conditions, in order to prevent the oscillator from stopping, two clocks are used for sampling.
3.7
Power-on Configuration Monitor Reset
In the power-on configuration process, there is a configuration monitoring circuit inside the chip, if the power-on configuration
time is too long, or the power-on configuration into a certain state can not be reconfigured, the internal monitoring circuit from
the configuration to start timing, if more than the setting time, the monitoring circuit reset configuration module, so that the
configuration module reconfiguration process. In case the system enters an unpredicted state when powered up.
The monitoring circuit operates at LSI (125KHz), the default monitoring time is 65ms, and if the 32.768KHz crystal oscillator
is selected, the monitoring time is 2.1s.