ST7FL15F1MAE STMICROELECTRONICS [STMicroelectronics], ST7FL15F1MAE Datasheet - Page 39

• Manufacturer Part Number: ST7FL15F1MAE
• Description: 8-bit MCU for automotive with single voltage Flash/ROM memory, data EEPROM, ADC, 5 timers, SPI
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

POWER SAVING MODES (cont’d)
Figure 25. ACTIVE HALT Mode Flowchart
Notes:
1. This delay occurs only if the MCU exits ACTIVE HALT
mode by means of a RESET.
2. Peripherals clocked with an external clock source can
still be active.
3. Only the RTC1 interrupt and some specific interrupts
can exit the MCU from ACTIVE HALT mode. Refer to
Table 5, “Interrupt Mapping,” on page 32
4. 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.
9.6 AUTO WAKE-UP FROM HALT MODE
Auto Wake-Up From Halt (AWUFH) mode is simi-
lar to HALT mode with the addition of a specific in-
ternal RC oscillator for wake-up (Auto Wake-Up
from Halt Oscillator). Compared to ACTIVE HALT
mode, AWUFH has lower power consumption (the
main clock is not kept running but there is no accu-
rate realtime clock available).
It is entered by executing the HALT instruction
when the AWUEN bit in the AWUCSR register has
been set.
(AWUCSR.AWUEN=0)
HALT INSTRUCTION
(Active Halt enabled)
N
INTERRUPT
Y
3)
256 OR 4096 CPU CLOCK
OR SERVICE INTERRUPT
FETCH RESET VECTOR
OSCILLATOR
PERIPHERALS
CPU
OSCILLATOR
PERIPHERALS
CPU
OSCILLATOR
PERIPHERALS
CPU
I BIT
I BIT
I BIT
N
CYCLE
RESET
Y
for more details.
DELAY
2)
2)
OFF
OFF
OFF
ON
ON
ON
ON
ON
ON
X
X
0
4)
4)
Figure 26. AWUFH Mode Block Diagram
As soon as HALT mode is entered and if the
AWUEN bit has been set in the AWUCSR register,
the AWU RC oscillator provides a clock signal
(f
er and a programmable prescaler controlled by the
AWUPR register. The output of this prescaler pro-
vides the delay time. When the delay has elapsed,
the AWUF flag is set by hardware and an interrupt
wakes up the MCU from HALT mode. At the same
time, the main oscillator is immediately turned on
and a 256 or 4096 cycle delay is used to stabilize
it. After this start-up delay, the CPU resumes oper-
ation by servicing the AWUFH interrupt. The AWU
flag and its associated interrupt are cleared by
software reading the AWUCSR register.
To compensate for any frequency dispersion of
the AWU RC oscillator, it can be calibrated by
measuring the clock frequency f
calculating the right prescaler value. Measurement
mode is enabled by setting the AWUM bit in the
AWUCSR register in Run mode. This connects
f
load timer, allowing the f
using the main oscillator clock as a reference time-
base.
AWU_RC
AWU_RC
f
AWU_RC
AWU RC
oscillator
divider
/64
to the input capture of the 12-bit Auto-Re-
). Its frequency is divided by a fixed divid-
prescaler/1 .. 255
to Timer input capture
AWUFH
AWU_RC
ST7L15, ST7L19
AWU_RC
to be measured
(ei0 source)
AWUFH
interrupt
and then
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