ST72F324BJ STMICROELECTRONICS [STMicroelectronics], ST72F324BJ Datasheet - Page 48

• Manufacturer Part Number: ST72F324BJ
• Description: 8-bit MCU, 3.8 to 5.5 V operating range with 8 to 32 Kbyte Flash/ROM, 10-bit ADC, 4 timers, SPI, SCI
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Power saving modes
8.3
48/188
Figure 24. Slow mode clock transitions
Wait mode
Wait mode places the MCU in a low power consumption mode by stopping the CPU.
This power saving mode is selected by calling the ‘WFI’ instruction.
All peripherals remain active. During Wait mode, the I[1:0] bits of the CC register are forced
to ‘10’, to enable all interrupts. All other registers and memory remain unchanged. The MCU
remains in Wait mode until an interrupt or reset occurs, whereupon 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
Figure 25. Wait mode flowchart
1. Before servicing an interrupt, the CC register is pushed on the stack. The I[1:0] bits of the CC register are
set to the current software priority level of the interrupt routine and recovered when the CC register is
popped.
25.
CP1:0
SMS
f
f
CPU
OSC2
N
WFI instruction
f
OSC2
Interrupt
00
Y
New Slow
frequency
request
/2
01
256 or 4096 CPU clock
f
Oscillator
Peripherals
CPU
I[1:0] bits
Oscillator
Peripherals
CPU
I[1:0] bits
Oscillator
Peripherals
CPU
I[1:0] bits
N
OSC2
Fetch reset vector
or service interrupt
Normal Run mode
/4
cycle delay
Y
Reset
f
OSC2
XX
on
on
on
10
10
on
on
off
on
off
on
(1)
request
ST72324B