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ADVANCED LOW POWER TECHNIQUES FOR SiM3L1XX DEVICES

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5.4.3. Refresh Rate

The LCD0 module on SiM3L1xx devices includes a programmable refresh rate by setting the CLKDIV bits in the

CLKCONTROL register. The LCD multiplexor mode must be taken into account when determining the prescaler

value. The LCD power consumption will scale proportionally with the refresh rate. For maximum power savings,

choose the slowest LCD refresh rate and the minimum LCD0 clock frequency that provides acceptable

performance for the application. For the least flicker, choose a fast LCD refresh rate.

5.5. Retention RAM

The retention RAM on SiM3L1xx devices is in eight 4 kB banks. All eight banks are available when not in PM8, but

can be individually powered down when in PM8. The current leakage of the RAM at higher temperatures may

increase, so disabling any unused banks when entering a low power mode may reduce system power

consumption.

For most applications, it is recommended to enable retention for all RAM banks. The specific bank containing the

stack pointer must be enabled to ensure proper code operation on an exit from PM8.

5.5.1. Adjusting the Stack Pointer with Keil µVision

With Keil µVision projects, the stack location can be controlled in the scatterfile. The default

linker_sim3l1xx_arm.sct scatterfile can be found in the C:\SiLabs\32bit\si32-x.y.z\si32Hal\sim3l1xx directory,

where x is the major si32HAL version, y is the minor version, and z is the trivial version.

Inside the scatterfile:

ARM_LIB_STACK (SI32_MCU_RAM_BASE + SI32_MCU_RAM_SIZE)

The value in the parentheses after the ARM_LIB_STACK label is the location of the stack pointer in memory.

Change this value as needed for the application and ensure this RAM bank has retention enabled.

5.5.2. Adjusting the Stack Pointer with the Precision32 IDE

In the Precision32 IDE, projects can use a custom linker script file edited manually or the IDE dialogs to modify the

stack pointer address. To add a custom linker script file manually:

Right-click on the project name in the Project Explorer view and select NewFolder. This folder must use the

linkscripts name.

Copy the link_template.ld file from the Precision32 installation directory ..\IDE\precision32\Wizards\linker to the

project’s linkscripts folder.

Open the project’s link_template.ld file and edit the stack line near the bottom of the file:

PROVIDE(_vStackTop = __top_${DATA} - ${STACK_OFFSET});

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