ST63156 datasheet(26/86 Pages) STMICROELECTRONICS

26 / 86 page

The STOP and WAIT modes have been imple-

mented in the ST631xx Core in order to reduce the

consumption of the device when the latter has no

instruction to execute. These two modes are de-

scribed in the following paragraphs. On ST631xx

as the hardware activated digital watchdog func-

tion is present the STOP instruction is de-activated

and any attempt to execute it will cause the auto-

matic execution of a WAIT instruction.

WAIT Mode

The configuration of the MCU in the WAIT mode

occurs as soon as the WAIT instruction is exe-

cuted. The microcontroller can also be considered

as being in a “software frozen” state where the

Core stops processing the instructions of the rou-

tine, the contents of the RAM locations and periph-

eral registers are saved as long as the power

supply voltage is higher than the RAM retention

voltage but where the peripherals are still working.

The WAIT mode is used when the user wants to re-

duce the consumption of the MCU when it is in idle,

while not losing count of time or monitoring of ex-

ternal events. The oscillator is not stopped in order

to provide clock signal to the peripherals. The tim-

ers counting may be enabled (writing the PSI bit in

TSCR register) and the timer interrupt may be also

enabled before entering the WAIT mode; this al-

lows the WAIT mode to be left when timer interrupt

occurs. If the exit from the WAIT mode is per-

formed with a general RESET (either from the acti-

vation of the external pin or by watchdog reset) the

MCU will enter a normal reset procedure as de-

scribed in the RESET chapter. If an interrupt is

generated during WAIT mode the MCU behaviour

depends on the state of the ST631xx Core before

the initialization of the WAIT sequence, but also of

the kind of the interrupt request that is generated.

This case will be described in the following para-

graphs. In any case, the ST631xx Core does not

generate any delay after the occurrence of the in-

terrupt because the oscillator clock is still available.

STOP Mode

On ST631xx the hardware watchdog is present

and the STOP instruction has been de-activated.

Any attempt to execute a STOP will cause the

automatic execution of a WAIT instruction.

Exit from WAIT Mode

The following paragraphs describe the output pro-

cedure of the ST631xx Core from WAIT mode

when an interrupt occurs. It must be noted that the

restart sequence depends on the original state of

the MCU (normal, interrupt or non-maskable inter-

rupt mode) before the start of the WAIT sequence,

but also of the type of the interrupt request that is

generated. In all cases the GEN bit of IOR has to

be set to 1 in order to restart from WAIT Mode.

Contrary to the operation of NMI in the RUN Mode,

the NMI is masked in WAIT Mode if GEN=0.

Normal Mode. If the ST631xx Core was in the

main routine when the WAIT instruction has been

executed, the ST631xx Core outputs from the wait

mode as soon as any interrupt occurs; the related

interrupt routine is executed and at the end of the

interrupt service routine the instruction that follows

the WAIT instruction is executed if no other inter-

rupts are pending.

Non-maskable Interrupt Mode. If the WAIT in-

struction has been executed during the execution

of the non-maskable interrupt routine, the ST631xx

Core outputs from the wait mode as soon as any

interrupt occurs: the instruction that follows the

WAIT instruction is executed and the ST631xx

Core is still in the non-maskable interrupt mode

even if another interrupt has been generated.

Normal Interrupt Mode. If the ST631xx Core was

in the interrupt mode before the initialization of the

WAIT sequence, it outputs from the wait mode as

soon as any interrupt occurs. Nevertheless, two

cases have to be considered:

- If the interrupt is a normal interrupt, the inter-

rupt routine in which the WAIT was entered will

be completed with the execution of the instruc-

tion that follows the WAIT and the ST631xx

Core is still in the interrupt mode. At the end of

this routine pending interrupts will be serviced

in accordance to their priority.

- If the interrupt is a non-maskable interrupt, the

non-maskable routine is processed at first.

Then, the routine in which the WAIT was en-

tered will be completed with the execution of

the instruction that follows the WAIT and the

ST631xx Core is still in the normal interrupt

mode.

Notes :

If all the interrupt sources are disabled, the restart

of the MCU can only be done by a Reset activation.

The Wait instruction is not executed if an enabled

interrupt request is pending. In the ST631xx the

hardware activated digital watchdog function is

present. As the watchdog is always activated the

STOP instruction is de-activated and any attempt

to execute the STOP instruction will cause an exe-

cution of a WAIT instruction.

WAIT & STOP MODES

ST63140,142,126,156

22/82

ST63156 数据表(PDF) 26 Page - STMicroelectronics

ST63156 数据表(HTML) 26 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

数据表下载