Blackfin Deep Sleep with RTC Stopwatch Wakeup

part1.c

// ISTAT Register Bit Definitions
#define RTC_INT_CLEAR 0x807F
#define RTC_WRITE_COMPLETE 0x8000

// PREN Register Bit Definitions
#define RTC_PRESCALER_ENABLE 0x0001

void Init_RTC(void)
{
  // Ensure clock is running at 1Hz by setting the prescalar
  *pRTC_ISTAT = RTC_WRITE_COMPLETE; // Clear write complete
  *pRTC_PREN = RTC_PRESCALER_ENABLE;
  // Wait for write to complete
  while (!(*pRTC_ISTAT&RTC_WRITE_COMPLETE)) {};

  // Perform setup of the RTC
  *pRTC_ISTAT = RTC_WRITE_COMPLETE; // Clear write complete
  *pRTC_STAT = 0; // Reset counter
  *pRTC_SWCNT = 0; // Make sure stopwatch is off
  *pRTC_ICTL = 0; // Deactivate all interrupt events
  // Wait for write to complete
  while (!(*pRTC_ISTAT&RTC_WRITE_COMPLETE)) {};
}

part2.c

// PLL Register Bit Definitions
#define PLL_PWDN 0x0020
#define PLL_BYPASS 0x0100

// IWR Register Bit Definitions
#define IWR_PLLWAKEUP 0x0001
#define IWR_RTCWAKEUP 0x0080

void Deep_Sleep(void) {
  unsigned int iReg;
  // Disable interrupts
  iReg = cli();

  // Program to wakeup only on an RTC event
  *pSIC_IWR = IWR_RTCWAKEUP;
  // Activate Deep Sleep, i.e. power down all internal clocks
  *pPLL_CTL = *pPLL_CTL|PLL_PWDN;
  // Idle processor to perform PLL programming
  idle();
           
  // Only wake from idle for PLL event
  *pSIC_IWR = IWR_PLLWAKEUP;
  // Reactivate the PLL to return to normal clock speed
  *pPLL_CTL = *pPLL_CTL&(~PLL_BYPASS);
  // Idle processor to perform PLL programming
  idle();

  // Enable interrupts
  sti(iReg);
}

part3.c

// RTC_ICTL Register Bit Definitions
#define RTC_STOPWATCH_IE 0x0001
#define RTC_ALARM_IE 0x0002
#define RTC_ONEHZTICK_IE 0x0004

// Setup the RTC
Init_RTC();
           
// Lets wait 5 seconds before we do anything
while (*pRTC_STAT < 5) {};
           
// Program stopwatch with 5 second countdown and enable the interrupt
*pRTC_ISTAT = RTC_INT_CLEAR; // Clear pending interrupt flags
*pRTC_SWCNT = 5;
*pRTC_ICTL = RTC_STOPWATCH_IE;
while (!(*pRTC_ISTAT & RTC_WRITE_COMPLETE)) {};
   
// Enter Deep Sleep Mode
Deep_Sleep();

part4.c

// Program alarm for 15 seconds from boot and enable the interrupt
*pRTC_ISTAT = RTC_INT_CLEAR; // Clear pending interrupt flags
*pRTC_ALARM = 15;
*pRTC_ICTL = RTC_ALARM_IE;
while (!(*pRTC_ISTAT & RTC_WRITE_COMPLETE)) {};

part5.c

// Enable the 1Hz interrupt
*pRTC_ISTAT = RTC_INT_CLEAR; // Clear pending interrupt flags
*pRTC_ICTL = RTC_ONEHZTICK_IE;
while (!(*pRTC_ISTAT & RTC_WRITE_COMPLETE)) {};

// Clear 1Hz flag
*pRTC_ISTAT = RTC_INT_CLEAR; // Clear pending interrupt flags

If you found your way here you might want to check out the article on my blog that goes with this code:
http://www.charles-keepax.co.uk/blog/BlackfinDeepSleep.html