IO control while in standby modes of STR711FR2H6

[hg-chen]

Posted on June 13, 2007 at 13:16

IO control while in standby modes of STR711FR2H6

[hg-chen]

Posted on June 13, 2007 at 10:23

according to reference manual, all the I/Os belonging to the kernel are forced to high impedance, so that it means the I/O can not be controled in standby mode,right? but the H/W design may use the I/O to control ex. power on/off,

Is there any suggestion (F/W or H/W design) to solve this problem! P.S. is this situation quite similar in waking up from stop mode? cause manual says external oscillator must be enabled when exiting from stop mode! it means STR711 can not be wake up but from turning on the external oscillator outside the MCU!

[kaouther]

Posted on June 13, 2007 at 13:16

Hello kuni,

Yes , during Standby mode all I/Os belonging to the kernel are forced to high impedance and system can exit this mode using the wakup pin, RTC alarm or Reset and no other I/Os can be used. if you need to control for example the main oscillator ON/OFF during standby mode or to command other hardware . It is possible to use the nRSTIN pin. When the system goes into standby mode, the nRSTIN pin will be automatically forced to low level. This pin could be used to command to the main oscillator and it will be disabled once system is in standby mode. When exiting the standby mode, the nRSTIN pin will be automatically activated and then the main oscillator will be activated too. Regarding the Stop mode, it is different because it is not possible to command for example to switch OFF/ON the main oscillator internally. You need an external interrupt to switch ON the main oscillator as described in the AN2100 ''STR71x Microcontroller Power Management ''. And you can command the main oscillator or other hardware using a GPIO pin which is not the case in Standby mode. Furthermore, for the stop mode, the external oscillator must be enabled when exiting from stop mode. Indeed, the MCU resumes program execution after a delay of 2048 clock CLK periods after the Stop mode wakeup event. And the source clock CLK is derived from the external oscillator, through the CK pin. That’s why, if the oscillator is not enabled and CLK is not available, the system will remain in stop mode. Hope it is clear. ;)