st72324bk STMicroelectronics, st72324bk Datasheet - Page 48

• Manufacturer Part Number: st72324bk
• Description: 3 V/5 V Range 8-bit Mcu With 4/8 Kbyte Rom, 10-bit Adc, Four Timers And Spi
• Manufacturer: STMicroelectronics

Power saving modes
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Halt mode recommendations
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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 level sensitiveness 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.
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 before executing 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).
ST72323 ST72323L