ST7LITE05 datasheet(40/122 Pages) STMICROELECTRONICS

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POWER SAVING MODES (Cont’d)

9.4.2.1 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 ex-

ternal interference or by an unforeseen logical

condition.

– For the same reason, reinitialize the level sensi-

tiveness of each external interrupt as a precau-

tionary 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 memo-

ry. For example, avoid defining a constant in

ROM with the value 0x8E.

– As the HALT instruction clears the I bit in the CC

to clear all pending interrupt bits before execut-

ing the HALT instruction. This avoids entering

other peripheral interrupt routines after executing

the external interrupt routine corresponding to

the wake-up event (reset or external interrupt).

ST7LITE05 数据表(PDF) 40 Page - STMicroelectronics