Power saving modes
ST72324xx-Auto
Halt mode recommendations
● Make sure that an external event is available to wake up the microcontroller from Halt
mode.
● When using an external interrupt to wake up the microcontroller, reinitialize the
corresponding I/O as “Input Pull-up with Interrupt” before executing the HALT
instruction. The main reason for this is that the I/O may be wrongly configured due to
external interference or by an unforeseen logical condition.
● For the same reason, reinitialize the sensitivity level of each external interrupt as a
precautionary measure.
● The opcode for the HALT instruction is 0x8E. To avoid an unexpected HALT instruction
due to a program counter failure, it is advised to clear all occurrences of the data value
0x8E from memory. For example, avoid defining a constant in ROM with the value
) 0x8E.
t(s ● As the HALT instruction clears the interrupt mask in the CC register to allow interrupts,
c the user may choose to clear all pending interrupt bits before executing the HALT
u instruction. This avoids entering other peripheral interrupt routines after executing the
d external interrupt routine corresponding to the wake-up event (reset or external
Obsolete Product(s) - Obsolete Pro interrupt).
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Doc ID 13841 Rev 1