AN2633 datasheet(40/48 Pages) STMICROELECTRONICS

40 / 48 page

Operating measurements

AN2633

40/48

After system power on, the system operates in Normal Run mode with the oscillator as

clock source.To indicate this, a LED connected to P9.1 is switched on.

When you push a button connected to pin P7.4, the system enters Idle mode with the

desired frequency and the LED connected to P9.1 is switched off.

The WDG is programmed to generate an interrupt every 3 seconds. Consequently,

after 3 seconds the WDG interrupt wakes up the system causing a LED connected to

P9.0 pin to toggle. This is used to indicate that the MCU is in RUN mode operating with

the selected (uncommented) frequency.

Test 28 and 29: LPMode_Idle_UART_Interrupt

First of all, you have to configure the Hyperterminal as follows:

Word Length = 7 Bits

Two Stop Bits

No parity

BaudRate = 115200 baud

Flow control: None

After system power on, the system operates in Normal Run mode with the oscillator as

clock source.To indicate this, a LED connected to P9.1 is switched on. When you push

a button connected to pin P7.4, the system enters Idle mode and UART0 sends 2

messages to the Hyperterminal ("UART - Hyperterminal communication without

hardware flow control") and ("to exit from low power mode you should send a byte from

Hyperterminal") and the LED connected to P9.1 is switched off.

The UART0 waits for a string from the hyperterminal that you must enter to wake-up the

MCU from Idle mode. A LED connected to P9.0 toggles to indicate that the system is in

Run mode and a message "STR91x is in Run mode" is sent to the hyperteminal.

Note:

Tests 28 and 29 work with any clock source (Oscillator, PLL: 48 MHz, PLL: 66 MHz and PLL:

96 MHz) except the RTC clock.

Test 30-31: LPMode_Idle_External_Reset

The system enters this mode as follows:

After system power on, the system operates in Normal Run mode with the oscillator as

clock source. To indicate this, a LED connected to P9.1 is switched on.

When you push a button connected to pin P7.4, the system enters Idle mode with the

desired frequency and the LED connected to P9.1 is switched off.

The system waits until you push RESET pin to wake-up from Idle mode. To indicate that

the power mode is Normal Run mode operating with the oscillator as clock source, a

LED connected to P9.1 pin is switched on.

3.2.9

Special Interrupt Run mode tests

Test 32: LPMode_Run_Special_Interrupt_IRQ

When you push a button connected to pin P7.4, the system enters Run mode and P9.0

pin toggles with the fRCLK=fMSTR/2 as frequency.

When a falling edge on EXINT group 0 line2 is detected, an interrupt is generated.

When entering the interrupt in Special Interrupt Run mode IRQ, a LED connected to

P9.1 pin is toggled. After servicing the interrupt routine, the MCU returns back to Run

mode and P9.0 pin is toggled.

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