Important changes to forums and questions
All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.
8 years, 4 months ago.
Are any peripherals active on power-up?
Hello,
some general newbie questions:-
1. When the mbed (LPC1114, LPC11U24, LPC1768 et al) comes out of reset, are any of the peripherals other than GPIO's active? e.g. I2C, USB or UART 2. Are any of the IRQ's associated with those peripherals active and assigned to any of the controller pins 3. If yes to any of the above, how can the unwanted peripherals be turned off (i.e. completely disabled because they will not be used in an application) 4. Is it a good idea to explicitly disable unwanted peripherals and if so how?
Thank you
AndrewR
1 Answer
8 years, 4 months ago.
1. Yes, a bunch are active.
2. No, while powered on, their irqs are disabled. I don't know if these mcus have an NMI pin and to what it is connected, that one might always be active, but none of the others will be.
3. By disabling them in the relevant register, see the MCU's reference manual.
4. It saves a bit of power. Especially if you want to use sleep mode it can be relevant. Although it won't make huge differences.
Looking at the 'start logic' functions, am I right in assuming that any inputs asserted LOW after reset trigger an IRQ that must be serviced?
posted by Andrew R 26 Nov 2015