Hello,
Please use Chapter 22 (Real-Time Clock Alarm Watchdog Persistent Bits) of the
i.MX28 Reference Manual. Basically to get the RTC working in power down mode
battery power (BATT) should be applied.
It is possible to configure the battery supply only for RTC domain:
when using a battery and a 5V power connection, the customer should apply the
same circuit connections in the "i.MX28 Reference Schematics", which are posted
on the Web.
This can be accomplished as follows:
1. Clear the DCDC_XFER bit (bit 5) in the HW_POWER_5VCTRL register, which will
disable the automatic transition to the DCDC converter (from the battery) when
5V power is removed.
2. Set the PWDN_5VBRNOUT bit (bit 7) in the HW_POWER_5VCTRL register, which will
automatically power down the device when 5V is removed.
3. Also, customers may want to set the PWDN_BRNOUT bit (bit 18) in the
HW_POWER_VDDIOCTRL, which will automatically power down the device when a VDDIO
brownout occurs. Note this only has effect if 5V is not present. After the VDDIO
brownout is set up, a VDDIO brownout will occur because the SW will not be setup
to run from the battery (via the DCDC converter) when 5V is removed, because the
DCDC_XFER bit will be cleared.
As for i.MX28 network - what do You mean? Please clarify in more details.
Have a great day,
Yuri
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