MPC5200 delayed bootup

[dondeoliveira]

MPC5200B processor sometimes (1 out of 10 power cycles or so) delays boot with no reads from FLASH from power on.  After a few minute or so processor comes up normally.  Only happens on one of my boards.  I checked power sequencing, reset and clocks and all looks good.  Anyone seen this behavior?

[jwittrock]

I finally found the problem causing problems on our own boards.

It has to do with the  TEST_SEL_1 pin which requires a pulldown resistor.

On our board, I blindly followed the Lite5200B eval board and used a 10k pulldown.  The problem is that I also have an FPGA connected to the LP bus.  The TEST_SEL_1 pin doubles as the TSIZ2 (transfer size) for non muxed mode of LP bus so this pin is routed to FPGA IO on our board.

The FPGA has weak pullups on its IO that are always active before configuration.  The combination of the weak pullup and and 10K pull down put the TEST_SEL_1 pin just below its switching threshold.  Low temperatures were enough to lower the temperature dependent FPGA pullups to the point of this pin going high during board reset.

Lowering the value of the pulldown to 1k fixed the problem.

[jwittrock]

Hello Don,

I am also experiencing this problem on several boards.  Just wondering if you were ever able to get an answer or if you have found the root of the problem you were seeing.

In our case, it looks to be temperature related.  At least on one of the boards where we have this problem, cooling the part below ambient temperature greatly increased the likelihood of it happening.  Once the part warms up, the problem goes away.

I have monitored CS going to flash and verified that when the problem occurs, no flash access is attempted by the processor.