Hey guys I just encountered a very strange problem on our mcf52277 board which is When I plug P&E cyclone debugger in everything is fine ,the board can boot up and run MQX RTOS normally . but once I remove that debugger the board just hardly can boot up. maybe one or two times in twenty times boot up tests. So I try to read the voltage of signal lines on that debugger, and use jumper wire to pull up or down these pins on my board one by one according to the debugger voltage, then I find out that once I short PSTCLK with 3.3V EVDD the board will boot up as expect, which is magical , and it even wont take effect if I connect a 100R resistor between PSTCLK and EVDD. I try to measure waveform of PSTCLK , it is 120MHZ Sin signal(why it's not square wave?), and it's also the frequency of Fsys. If I just disable the signal by pull up JTAG_EN pin. the board will back to normal too. but WHY?? I got verrrrrrrrrry confused , help me please!!
**I'm using a 1uf capacitor in my RC reset circuit, if I remove this cap , things will get better. maybe this problem is relate to the rise time of reset signal?
***I made a circuit that can generate reset signal after EVDD stablized which is not useful.
**** this is not a common issue but still occur with 5-10% probability
I would recommend customer to check the MCF5227x product errata file.
The SECF033: PLL Loss of Lock and Clock Jitter could be the root cause.
Please check the MCF5227 product silicon version.
Wish it helps.