1. Low Power Modes MTT48 V2.1 15 - 1 LOW POWER OPERATION

3. Low Power Modes MTT48 V2.1 15 - 3 Topics Effects of Low Power Modes WAIT STOP Low Power Operation Options

4. Low Power Modes MTT48 V2.1 15 - 4 General Discussion Some applications require idle or low power conditions Controller not required to perform any tasks Must be able respond to an event occurring and begin processing again –Can not remove power source Do not wish to consume excess power Examples: Automotive Factory automation

5. Low Power Modes MTT48 V2.1 15 - 5 General Discussion Two areas of concern MCU power usage External circuitry power usage External controller circuitry is application dependent and must be handled through software and/or hardware MCU has two software controlled low power modes WAIT STOP

6. Low Power Modes MTT48 V2.1 15 - 6 WAIT Instruction Instructs CPU Halt processing instructions Wait for an interrupt (or reset) –I Bit in CCR automatically cleared System Integration Module Disables CPU clock –Lowers power consumption All other MCU subsystems remain active and operate normally May be sources of interrupts (resets) that wake CPU

7. Low Power Modes MTT48 V2.1 15 - 7 CPU Wakeup To remove CPU from wait state External interrupt –IRQ1, IRQ2 MCU subsystem interrupt –DMA, SCI, SPI, TIM, etc. External reset –RESET Internal reset –COP, LVI NOTE: COP timer remains active (if enabled) during wait instruction –Will generate internal reset if not cleared occasionally

8. Low Power Modes MTT48 V2.1 15 - 8 CPU Wakeup Upon wakeup CPU will start exception processing –Interrupt –Reset Completes exception processing Starts program flow with instruction after WAIT –Unless reset occurred, goes to location pointed to by RESET vector No register contents, CPU or submodule, are affected

9. Low Power Modes MTT48 V2.1 15 - 9 STOP Instruction Instructs CPU Stop processing instructions Wait for an interrupt (or reset) –I Bit in CCR automatically cleared System Integration Module Disables crystal oscillator in CGM –Stops internal clock generation (CGMXCLK) –Stops all system clocks * Shutting down all MCU submodules Results in lowest power consumption mode * Some modules may have external clock sources Timer Interface Module - TCLK SPI (in slave mode) - SPSCK

10. Low Power Modes MTT48 V2.1 15 - 10 Exiting STOP To remove CPU from stop state External interrupt –IRQ1, IRQ2, or Port Interrupt External reset –RESET

11. Low Power Modes MTT48 V2.1 15 - 11 Exiting Upon exiting Keeps system clocks disabled for 4096 CGMOUT clock cycles –Allows oscillator circuit to stabilizeSee SSREC bit in Mask Option Register CPU will start exception processing Completes exception processing Starts program flow with instruction after STOP –Unless reset occurred, goes to location pointed to by RESET vector No register contents, CPU or submodule, are affected Except BCS bit in CGM’s PLL Control Register –Cleared to select crystal oscillator vs. PLL circuit

12. Low Power Modes MTT48 V2.1 15 - 12 STOP Enable/Disable Mask Option register(MOR) STOP instruction disable –Prevents execution of STOP –STOP treated as illegal opcode Generates reset 1 = STOP enabled 0 = STOP disabled NOTE: Erased state of MOR has STOP disabled NOTE: Mask Option Register contents cannot be changed by program Bits set or cleared at time of EPROM/OTP programming RESET: UNAFFECTED BY RESET WRITE: MOR READ: 0 LVISTOP LVIRST LVIPWR SSREC SEC STOP COPD

13. Low Power Modes MTT48 V2.1 15 - 13 Low Power Options Apart from WAIT and STOP instructions, power consumption may be lowered by disabling submodules when not needed Disabled completely –ENSCI bit in SCI module –SPE bit in SPI module –LVIPWR bit in LVI –COP bit in MOR register Partially disabled –TIM timer channels –DMA channels

14. Low Power Modes MTT48 V2.1 15 - 14 Disabling submodules prior to WAIT instruction can reduce power consumption during wait mode also Additionally, if slower system clock frequency can be used Switch to crystal oscillator circuit –BCS bit in CGM Turn off PLL circuitry –PLLON bit in CGM Do not forget to switch back upon exiting wait mode Low Power Options

15. Low Power Modes MTT48 V2.1 15 - 15 Summary A number of options to reduce power consumption Disable submodules WAIT instruction WAIT instruction, plus disabling submodules STOP instruction STOP puts MCU in lowest power consumption mode