Champs,
I received a new custom board and am having some issues with getting the MCU up and running. The primary symptoms of issues are that
a) XRSn is only rising to about 2V despite having a 4.7k Pull up resistor to 3.3V. It is not cycling periodically as if the processor is in reset. I have verified the resistor value with a multimeter.
b) There is no voltage on the 1.2V rail. Note that this is the 56 pin package which does not pinout VREGENz.
Here is what I know that are good signs:
c) The 3.3V rail going into the MCU is correct and stable on both VDDA and VDDIO.
d) The MCU does seem to be up and running to some degree as there is serial data on the TMS pin. It is not a great waveform as it goes in and out of being a good square wave.
This schematic around the MCU is mostly ported from an existing working design with a F280049C 56-pin package so it is surprising to have any issues. There have been significant layout changes and modifications to the JTAG circuit, but the data above has been collected without an emulator connected so I do not expect a major impact from that. The JTAG traces are cleanly routed and are at most a couple of inches long.
What is a good place to start to determining why XRSn is not getting to 3.3V and there is not a voltage on the VDD pins?