ST72561J9-Auto STMicroelectronics, ST72561J9-Auto Datasheet - Page 67

• Manufacturer Part Number: ST72561J9-Auto
• Description: 8-bit MCU for automotive
• Manufacturer: STMicroelectronics

Specifications of ST72561J9-Auto

• Hdflash Endurance: 100 cycles, data retention 20 years at 55 °C
• 5 Power Saving Modes: halt, auto wake up from halt, active halt, wait and slow

ST72561-Auto
7.5
Halt mode recommendations
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Active halt mode
ACTIVE HALT mode is the lowest power consumption mode of the MCU with a real time
clock available. It is entered by executing the ‘HALT’ instruction when MCC/RTC interrupt
enable flag (OIE bit in MCCSR register) is set and when the AWUEN bit in the AWUCSR
register is cleared
Table 22.
The MCU can exit ACTIVE HALT mode on reception of the RTC interrupt and some specific
interrupts (see
RESET a 4096 or 256 CPU cycle delay occurs (depending on the option byte). After the
start up delay, the CPU resumes operation by servicing the interrupt or by fetching the reset
vector which woke it up (see
When entering ACTIVE HALT mode, the I[1:0] bits in the CC register are are forced to ‘10b’
to enable interrupts. Therefore, if an interrupt is pending, the MCU wakes up immediately.
In ACTIVE HALT mode, only the main oscillator and its associated counter (MCC/RTC) are
running to keep a wake-up time base. All other peripherals are not clocked except those
which get their clock supply from another clock generator (such as external or auxiliary
oscillator).
The safeguard against staying locked in ACTIVE HALT mode is provided by the oscillator
interrupt.
MCCSR
OIE bit
Make sure that an external event is available to wake up the microcontroller from Halt
mode.
When using an external interrupt to wake up the microcontroller, reinitialize the
corresponding I/O as “Input Pull-up with Interrupt” before executing the HALT
instruction. The main reason for this is that the I/O may be wrongly configured due to
external interference or by an unforeseen logical condition.
For the same reason, reinitialize the level sensitiveness of each external interrupt as a
precautionary measure.
The opcode for the HALT instruction is 0x8E. To avoid an unexpected HALT instruction
due to a program counter failure, it is advised to clear all occurrences of the data value
0x8E from memory. For example, avoid defining a constant in ROM with the value
0x8E.
As the HALT instruction clears the interrupt mask in the CC register to allow interrupts,
the user may choose to clear all pending interrupt bits before executing the HALT
instruction. This avoids entering other peripheral interrupt routines after executing the
external interrupt routine corresponding to the wake-up event (reset or external
interrupt).
0
1
MCC/RTC low power mode selection
Table
HALT mode
ACTIVE HALT mode
(Section 7.6.1: Register
16) or a RESET. When exiting ACTIVE HALT mode by means of a
Power saving mode entered when HALT instruction is executed
Figure
Doc ID 12370 Rev 8
28).
description)
Power saving modes
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