AN3316 datasheet(28/42 Pages) STMICROELECTRONICS

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Device modes

AN3316

28/42

Doc ID 18232 Rev 2

For the HW steps, refer to Chapter : Common HW aspects. Now, see in details operation

done for each phase:

RUN0 mode:

Mode config in STOP:

ME_STOP_MC.CFLAON = 1

(code Flash in Power-Down)

ME_STOP_MC.DFLAON = 2

(data Flash in Low Power mode)

In this way, at STOP exiting, Flash startup from Power-Down to Normal mode takes few

usecs

ME_ STOP_MC.XOSC0ON = 1 (turn-on the XTAL)

The XTAL is maintained on in STOP in order to clock CAN protocol handler: in this way

PLL jitter issues are avoided

ME_ STOP_MC.SYSCLK = 0

(set FIRC as device system clock)

Periphs mode config STOP mode:

ME_RUN_LP0.STOP = 1 (activate low power peripheral configuration ’0’ in STOP)

ME_PCTL[16].LP_CFG = 0 to select the low power peripheral configuration ’0’ for

FlexCAN0 identified by offset = 16 (refer to figure x)

Timer config:

See Step 5 (RUN0

 HALT mode)

Request transition to RUN0 mode:

in case of RUN0

 STOP transition, these two register writing should be done:

ME.MCTL.R = 0xA0005AF0

ME.MCTL.R = 0xA000A50F

RUN0

 STOP mode:

Once a valid mode transition request is detected, the transition starts. Here, device

switches-on/off modules and peripherals without CPU intervention.

It is possible to check for transition completion through mode Transition Status bit:

while (ME.GS.MTRANS != 0)

//transition ongoing

...

//transition completed

...

in order to prevent code stucking waiting for transition completion, it could be better to

check transition timing through a timer. As, in this case, as there aren’t any slow-start-

up peripherals to switch-on, timeout could be considered equal to few clock cycles.

STOP mode:

At the end of the transition, device enters in STOP mode with core switched-off,

FlexCAN0 switched-on and CFLASH in Power Down. All others peripherals are

maintained in the same status of the RUN0 mode.

At this point, if a FlexCAN0 interrupt event is generated, the device, automatically,

starts the transition to go back to the previous RUN0

transition STOP

 RUN0 mode:

During the STOP

 RUN0 transition, the device automatically restores the

peripherals/modules as they were configured before entering in STOP. So, core is

already on and CFLASH comes back to Normal mode

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