Embedded RTC

[keisukewatanabe]

Dear support,

I am not going to use the embedded RTC of Vybfid.

The RTC, does it have that can be used for purposes other than such as retention time?

(As EXTAL32 terminal = Open/XTAL32 terminal = GND, or will not affect the basic operation of the RTC other than Vybrid?)

Best regards,

Keisuke

[naoumgitnik]

Dear Keisuke,

Regarding using the RTC (reral Time Clock) block for another purpose - for example for what, please?

Sincerely, Naoum Gitnik.

[keisukewatanabe]

Dear Naoum,

I do not use the RTC.

I want to know whether this RTC is used for (expect the clock) the purpose of my not knowing it.

Best regards,

Keisuke

[anthony_huereca · Accepted solution]

Hi Keisuke,

  To make sure we understand the question correctly, you do not want to populate an external 32KHz clock (as you are not using the RTC feature), and want to know what other effects that would have?

  The external RTC clock can also be used as a clock counter for the LPTimer module, and used in some security applications with tamper. You also lose the ability to clock the core off that clock. You can see where that clock goes in Figure 9-1 of the RM.

-Anthony

[keisukewatanabe]

Dear Naoum,

Let me confirm again.

If I do not use the security block (expect eFUSE and JTAG), is it correct in the following?

1. EXTAL32 pin = OPEN

2. XTAL32 pin = GND

Best regards,

Keisuke Watanabe

[naoumgitnik]

Dear Keisuke,

Yes, when the security block is not used, no external 32kHz crystal is needed and the pin connections you proposed would work.

Please, be careful, though – as per the Figure 9-1 of the Reference Manual, the 2 intermediate clocks, LPRC and LFSR, are used for the LPTMR counter and PLL4 blocks, respectively. If you need them for your application, the only alternative would be using the built-in 128kHz IRC (i.e. crystal-less) oscillator instead; it is less accurate but might be good enough for your application.

Sincerely, Naoum Gitnik.