We are using T1024 Processor on our design.
Some time we are facing issues on the NOR Flash booting immediately after power on the board.
The booting stuck and no response on the CLI Console at the PC. On our multiple power on/off trials, at least half of the times we could see this failure cases.While digging more we found few of the below observations.
Few observations at the board related with this:
1. Voltage rail seq is as follows:
On sequence - First - 3.3V,2.5V,1.8V; Second - 1.0V, S1VDD, 1.5V (after 10ms from First); Third - 1.35V & VTT (7ms after 2nd)
Off Sequence - First - All rails except 1.0V; Second - 1.0V (after 40ms from First)
2. 3.3V ramping slowly compare with 1.8V & 2.5V (please refer the attached waveform).We can make the 3.3V ramp faster little more through the regulator CC option, but for 1.8V & 2.5V, we cannot its a fixed. So we may need to live with this. ("...RAMP.png")
3. CPLD, powered by 3.3V, releases all reset lines, once it received a power good (after all power rails crossing its power good and stable high) from the sequencer. There is a 3.3V to 1.8V conversion for the CPU_RESET_L. Due to the 1.8V faster ramp, we are seeing a spikes on the CPU_RESET_L, before a stable reset release. Please refer the attached wavefrom & circuit(CPU_RESET.png, All_resets.png). Would this be one of the reasons for the booting stuck?
4. HRESET is always low when the booting is not happening. Also the buffer control signal BCTL is low.
Is it what expected? While booting is properly happening, i could see a High on both HRESET and BCTL pins.
5. Attached the Reset sequence waveform both for the Boot pass and fail conditions."..._RST-SEQ_bootfails.png", "..._RST-SEQ_bootpass.png"
We are trying to find the root cause for this booting stuck while power up.
Kindly give your valuable input on this issues.