My prototype Blackfin 533 board is working well however I want to advance the design to incorporate an external supply for VDDINT and utilise the hibernate mode. I've read through EE-334 and have studied the examples but am unsure about one aspect of Option #1 from EE-334. Option #1 states that it does not support an RTC wakeup but I don't understand why not.
If 00 is written to the FREQ[1:0] of VR_CTL during FULL ON mode then
i) the output transitions of VROUT will cease
ii) Pin 4 of U7 will assert the shutdown
iii) VDDINT will drop
iv) the processor core will go into hibernation mode
After the RTC timer expires,
v) an internal processor reset will be asserted
vi) VR_CTL will then be set to its default state (0x00DB)
vii) VROUT will resume its transitions
viii) SHDWN goes high
ix) VDDINT is applied to the core
x) the processor will boot according to BMODE[0:1]
In my design, VDDEXT will always be 3.3V. The external buck regulator used is an ADSP2302 and the PGOOD pin can be brought round to the reset chip to generate a hardware reset if required.
Hope you can point out what I'm missing. Many thanks for you help