ST72F321J ST Microelectronics, ST72F321J Datasheet - Page 40

• Manufacturer Part Number: ST72F321J
• Description: 8-BIT MCU
• Manufacturer: ST Microelectronics

www.DataSheet4U.com
DataSheet
ST72321J
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’ 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
40/179
4
U
.com
Figure
23.
www.DataSheet4U.com
Figure 23. WAIT Mode Flow-chart
Note:
1. Before servicing an interrupt, the CC register is
pushed on the stack. The I[1:0] bits of the CC reg-
ister are set to the current software priority level of
the interrupt routine and recovered when the CC
register is popped.
WFI INSTRUCTION
N
INTERRUPT
Y
OR SERVICE INTERRUPT
FETCH RESET VECTOR
256 OR 4096 CPU CLOCK
OSCILLATOR
PERIPHERALS
CPU
I[1:0] BITS
OSCILLATOR
PERIPHERALS
CPU
I[1:0] BITS
OSCILLATOR
PERIPHERALS
CPU
I[1:0] BITS
N
CYCLE DELAY
www.DataSheet
www.DataSheet
www.DataSheet
www.DataSheet4U
RESET
Y
XX
OFF
OFF
ON
ON
ON
ON
ON
ON
ON
10
10
1)
4U
4U.com
4U
.com
.com
.com