ST7232A
POWER SAVING MODES
(Cont鈥檇)
8.4.2.1 Halt Mode Recommendations
鈥?Make sure that an external event is available to
wake up the microcontroller from Halt mode.
鈥?When using an external interrupt to wake up the
microcontroller, reinitialize the corresponding I/O
as 鈥淚nput Pull-up with Interrupt鈥?before executing
the HALT instruction. The main reason for this is
that the I/O may be wrongly configured due to ex-
ternal interference or by an unforeseen logical
condition.
鈥?For the same reason, reinitialize the level sensi-
tiveness of each external interrupt as a precau-
tionary measure.
鈥?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 memo-
ry. For example, avoid defining a constant in
ROM with the value 0x8E.
鈥?As the HALT instruction clears the interrupt mask
in the CC register to allow interrupts, the user
may choose to clear all pending interrupt bits be-
fore executing the HALT instruction. This avoids
entering other peripheral interrupt routines after
executing the external interrupt routine corre-
sponding to the wake-up event (reset or external
interrupt).
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