Hello,
I have a project using the RTC_B of the MSP430F5659. The processor runs via the DCO. The XT2 crystal is intended for USB operation only to save energy. XT1 is connected to a watch crystal
The RTC_B provides a clock. The time is output in the menu. The RTCRDYIFG flag triggers an interrupt which wakes up the processor and updates the time again. When a key is pressed, the menu is also redrawn and thus the time is also output.
If I initialize UCS as follows the whole thing works fine:
while (BAKCTL & LOCKBAK) // Unlock XT1 pins for operation
BAKCTL &= ~(LOCKBAK);
UCSCTL6 |= XCAP_3; // Lastkapazität auf ca. 12 pF gesetzt
UCSCTL6 &= ~(XT1OFF); // Set XT1 & XT2 On
do // Loop until XT1,XT2 & DCO stabilizes
{
UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + XT1HFOFFG + DCOFFG); // Clear XT2,XT1,DCO fault flags
SFRIFG1 &= ~OFIFG; // Clear fault flags
}
while (SFRIFG1 & OFIFG); // Test oscillator fault flag (OSC Fault Flag set again?)
UCSCTL6 |= XT1DRIVE_3; // drive strenth max
UCSCTL6 &= ~XT2OFF; // Turn on XT2
UCSCTL4 |= SELA__XT1CLK; // Set XT1CLK as ACLK clock source --> RTC
UCSCTL5 |= DIVA__1; // Set ALCK source divider to 1
but of course the XT2 is running. However, if I change the two UCSCTL6 lines after the while loop to:
UCSCTL6 |= XT1DRIVE_3 + XT2OFF; //switch off XT2 // UCSCTL6 &= ~XT2OFF;
the XT2 is turned off now and I get a strange behavior from the RTC_B.
The periodic redraw after the RTCRDYIFG interrupt still works. The time is updated. However, when I press the key, I cannot read time from the registers RTCSEC, RTCMIN and RTCHOUR. I only read 0x00 and even after a write attempt I still read 0x00. However, reading after the interrupt still works.
The function, which generates the time-string is the same.
Does anyone have any ideas? I don't see a XT2 function for RTC_B in the data sheet.
Regards
Stefan
