Specifications

ST72104Gx, ST72215Gx, ST72216Gx, ST72254Gx
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POWER SAVING MODES (Cont’d)
8.3 WAIT MODE
WAIT mode places the MCU in a low power con-
sumption mode by stopping the CPU.
This power saving mode is selected by calling the
“WFI” ST7 software instruction.
All peripherals remain active. During WAIT mode,
the I bit of the CC register is forced to 0, to enable
all interrupts. All other registers and memory re
-
main unchanged. The MCU remains in WAIT
mode until an interrupt or Reset occurs, whereup
-
on the Program Counter branches to the starting
address of the interrupt or Reset service routine.
The MCU will remain in WAIT mode until a Reset
or an Interrupt occurs, causing it to wake up.
Refer to Figure 18.
Figure 18. WAIT Mode Flow-chart
Note:
1. Before servicing an interrupt, the CC register is
pushed on the stack. The I bit of the CC register is
set during the interrupt routine and cleared when
the CC register is popped.
WFI INSTRUCTION
RESET
INTERRUPT
Y
N
N
Y
CPU
OSCILLATOR
PERIPHERALS
I BIT
ON
ON
0
OFF
FETCH RESET VECTOR
OR SERVICE INTERRUPT
CPU
OSCILLATOR
PERIPHERALS
I BIT
ON
OFF
1
ON
CPU
OSCILLATOR
PERIPHERALS
IBIT
ON
ON
X
1)
ON
4096 CPU CLOCK CYCLE
DELAY