STR910FAZ32H6T STMICROELECTRONICS [STMicroelectronics], STR910FAZ32H6T Datasheet - Page 23

• Manufacturer Part Number: STR910FAZ32H6T
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

STR91xFAx32 STR91xFAx42 STR91xFAx44
3.11
3.11.1
3.11.2
Note:
3.11.3
Flexible power management
The STR91xFA offers configurable and flexible power management control that allows the
user to choose the best power option to fit the application. Power consumption can be
dynamically managed by firmware and hardware to match the system’s requirements.
Power management is provided via clock control to the CPU and individual peripherals.
Clocks to the CPU and peripherals can be individually divided and gated off as needed. In
addition to individual clock divisors, the CCU master clock source going to the CPU, AHB,
APB, EMI, and FMI can be divided dynamically by as much as 1024 for low power operation.
Additionally, the CCU may switch its input to the 32.768 kHz RTC clock at any time for low
power.
The STR91xFA supports the following three global power control modes:
●
●
●
A special mode is used when JTAG debug is active which never gates off any clocks even if
the CPU enters Idle or Sleep mode.
Run mode
This is the default mode after any reset occurs. Firmware can gate off or scale any individual
clock. Also available is a special Interrupt Mode which allows the CPU to automatically run
full speed during an interrupt service and return back to the selected CPU clock divisor rate
when the interrupt has been serviced. The advantage here is that the CPU can run at a very
low frequency to conserve power until a periodic wake-up event or an asynchronous
interrupt occurs at which time the CPU runs full speed immediately.
Idle mode
In this mode the CPU suspends code execution and the CPU and FMI clocks are turned off
immediately after firmware sets the Idle Bit. Various peripherals continue to run based on
the settings of the mask registers that exist just prior to entering Idle Mode. There are 3
ways to exit Idle Mode and return to Run Mode:
●
●
●
It is possible to remain in Idle Mode for the majority of the time and the RTC can be
programmed to periodically wake up to perform a brief task or check status.
Sleep mode
In this mode all clock circuits except the RTC are turned off and main oscillator input pins
X1_CPU and X2_CPU are disabled. The RTC clock is required for the CPU to exit Sleep
Run Mode: All clocks are on with option to gate individual clocks off via clock mask
registers.
Idle Mode: CPU and FMI clocks are off until an interrupt, reset, or wake-up occurs.
Pre-configured clock mask registers selectively allow individual peripheral clocks to
continue run during Idle Mode.
Sleep Mode: All clocks off except RTC clock. Wake up unit remains powered, PLL is
forced off.
Any reset (external reset pin, watchdog, low-voltage, power-up, JTAG debug command)
Any interrupt (external, internal peripheral, RTC alarm or interval)
Input from wake-up unit on GPIO pins
Functional overview
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