how to use RTC of IMX6?

[翔李]

HI,

I design a board on IMX6DUAL,but I am not sure of RTC.How to use RTC?

Is it mean that RTC embeded in imx6, I can only supply a 32.768khz external oscillator or a crystal or a crystal using the internal oscillator amplifier ? where is the power-pin to supply for RTC when IMX6 power off? Is it VDD_SVNS_IN?

If I not like to use the RTC of IMX6,can I use a RTC IC external?like PCF8563,with its 32.768KHZ and 3.3v battery?

[gusarambula]

Hello 翔李,

You are correct, there are three possible ways to feed the RTC: using a crystal, through an external oscillator or by using the on-chip loose tolerance 40Khz oscillator.

The voltage requirements for XTALI can be found on table 21 of the i.MX6D Datasheet (link below).

https://www.nxp.com/docs/en/data-sheet/IMX6DQCEC.pdf

You can find more details on the requirements for the RTC clock (crystal or oscillator input) on Table 2.7 of the HW Design Guide (link below)

https://www.nxp.com/docs/en/user-guide/IMX6DQ6SDLHDG.pdf

You may use the PCF8563 as an external RTC with the i.MX6. In that case using the on-chip oscillator should be okay since the precise RTC is being handled externally.

I hope this information helps!

Regards,

[翔李]

thanks.

if I use PCF8563,with its 32.768khz,iic to imx6,is it necessary to add 32.768khz in rtc_xtal pin of imx6?

or can I add 32.768khz in rtc_xtal of imx6,but no 32.768khz with PCF8563,when use PCF8563?

[gusarambula]

Hello 翔李,

There are a couple of options. The i.MX6 RTC clock must be provided, but it may be provided by the internal on-chip oscillator if you wish to use the PCF8563 to keep the RTC. The PCF8563 which would need a 32.768 kHz crystal.

Another alternative could be using the 32.768 kHz crystal on the i.MX6 directly and using an output from the i.MX6 with the 32.768 kHz clock signal to feed the PCF8563.

Either way you would need a 32.768 kHz or oscillator if you wish to keep an accurate RTC.

I hope this helps!

Regards,