Power and Time

Power in the news

• Facebook
  • Forest City, NC, US
  • Cold storage data center
  • Open Compute Project
• Be unreliable to save power

Power in a µcontroller

Let’s look at some nice pictures from the ECE 3724 Chapter 8 PIC24 Startup to look at power on the PIC24.

Power requirements, p. 11

• Stable power: VDD, VSS, &l VCAP
• Decoupling capacitors filter power supply to the chip

Clock options, p. 15-16

Clock frequency and power usage are proportional. The less power used, the longer the batteries last.

• Several possibilites
  • Internal oscillator
  • Crystal
  • External clock
• Means of varying the frequency
  • cross-rhytm on youtube
  • Tuner for the Fast FC oscillator
  • Dividers (postscalers)
  • Phase locked loop
• Spreadsheet illustration
• PIC24H Oscillator documentation

Reset, p. 25-26

The PIC24 can be reset in many ways.

• Program action
  • RESET instruction
  • bad instructions
• Reset (MCLR) input
• Power on / brown out
• Watchdog timer
• Interrupt (pin change) during sleep or idle mode

Watchdog Timer, p. 28-32

The watchdog timer can be used to save power, by putting the processor asleep for short periods of time, or to prevent software malfunctions. The Pathfinder mission to Mars was rescued by a watchdog timer.