C8051F960-B-GM Datasheet, PDF (257/492 Pages) Silicon Laboratories – Ultra Low Power 128K, LCD MCU Family

C8051F96x
19. Power Management
C8051F96x devices support 6 power modes: Normal, Idle, Stop, Low Power Idle, Suspend, and Sleep.
The power management unit (PMU0) allows the device to enter and wake-up from the available power
modes. A brief description of each power mode is provided in Table 19.1. Detailed descriptions of each
mode can be found in the following sections.
Table 19.1. Power Modes
Power Mode
Description
Normal
Device fully functional
Wake-Up
Sources
N/A
Power Savings
Excellent MIPS/mW
Idle
Stop
All peripherals fully functional.
Very easy to wake up.
Legacy 8051 low power mode.
A reset is required to wake up.
Low Power Improved Idle mode that uses
Idle
clock gating to save power.
Any Interrupt.
Any Reset.
Any Interrupt
Good
No Code Execution
Good
No Code Execution
Precision Oscillator Disabled
Very Good
No Code Execution
Selective Clock Gating
Suspend
Sleep
Similar to Stop Mode, but very fast
wake-up time and code resumes
execution at the next instruction.
SmaRTClock,
Port Match,
Comparator0,
RST pin,
Pulse Counter
VBAT Monitor.
Very Good
No Code Execution
All Internal Oscillators Disabled
System Clock Gated
Ultra Low Power and flexible
wake-up sources. Code resumes
execution at the next instruction.
SmaRTClock,
Port Match,
Comparator0,
RST pin,
Pulse Counter
VBAT Monitor.
Excellent
Power Supply Gated
All Oscillators except SmaRT-
Clock Disabled
In battery powered systems, the system should spend as much time as possible in sleep mode in order to
preserve battery life. When a task with a fixed number of clock cycles needs to be performed, the device
should switch to normal mode, finish the task as quickly as possible, and return to sleep mode. Idle mode,
low power idle mode, and suspend mode provide a very fast wake-up time; however, the power savings in
these modes will not be as much as in sleep Mode. Stop Mode is included for legacy reasons; the system
will be more power efficient and easier to wake up when idle, low power idle, suspend, or sleep mode is
used.
Although switching power modes is an integral part of power management, enabling/disabling individual
peripherals as needed will help lower power consumption in all power modes. Each analog peripheral can
be disabled when not in use or placed in a low power mode. Digital peripherals such as timers or serial
busses draw little power whenever they are not in use. Digital peripherals draw no power in Sleep Mode.
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