Hi there,
I am trying to use an external 32KHz clock on the EXTAL pin as the clock reference for the internal RTC in the 5606B chip.
I am working according to this table from the reference manual:
My OSC32_EXTAL pin is connected to a 32KHz clock (which is ticking correctly, verified with a scope), and OSC32_XTAL is grounded.
When I am setting the bypass bit in the SXOSC_CTL register (as per line 2) the RTC clock does not tick at all, and the API interrupt is never called, and when I set is to enable, and I am supposedly at line 4 of the table, the interrupt is called instead of every second, every ~1.3 seconds.
I measured the internal 32KHz clock using the CMU, and got a result of ~24KHz, which is consistent with the RTC behavior.
Tried on another board and replicated the results.
Any ideas on what I am doing wrong?
Thanks in advance.
Hi,
Do you use your own board or some FSL one?
I have tested the SXOSC with the RTC to generate 1sec interrupt on the TRK-MPC5606B and it worked if the SXOSC is enabled with SXOSC_CTL[OSCON] bit. The 32768Hz is fed to EXTAL pin and 1sec is properly generated.
BR, Petr
Thank you for the reply.
I am using my own board, but like I said I verified the 32768Hz input with a scope.
Did you measure the 1 second frequency with an external indication / stopwatch? I am also getting the interrupts, only they are about 0.75 seconds apart instead of 1 second.
In addition, does bypass mode works for you?
Thanks again,
Gilad
Hi,
I measured the pin toggling with the scope, get 1sec exactly.
It is true that bypass mode worked in a strange way. The SXOSC_CTL[OSCON] has to be set too when bypass was set. In that case RTC was working too.
BR, Petr