
Obsolete Product(s) - Obsolete Product(s)
Obsolete Product(s) - Obsolete Product(s)
Power saving modes
ST7LITEUS2, ST7LITEUS5
Figure 20.
Wait mode flowchart
1.
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.
8.4
Active-halt and Halt modes
Active-halt and Halt modes are the two lowest power consumption modes of the MCU. They
are both entered by executing the ‘HALT’ instruction. The decision to enter either in Active-
halt or Halt mode is given by the LTCSR/ATCSR register status as shown in the following
table:
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
0
ON
CPU
OSCILLATOR
PERIPHERALS
I BIT
ON
ON
X
1)
ON
64 CPU CLOCK CYCLE
DELAY
Table 14.
Enabling/disabling Active-halt and Halt modes
LTCSR TBIE
bit
ATCSR OVFIE
bit
ATCSRCK1 bit ATCSRCK0 bit
Meaning
0
x
x
0
Active-halt mode disabled
0
0
x
x
0
1
1
1
1
x
x
x
Active-halt mode enabled
x
1
0
1
Obsolete Product(s) - Obsolete Product(s)