MCF5329 (MCF5xxx) + SDR DRAM = lockup, anyone else?

Discussion created by TomE on Sep 20, 2010
Latest reply on Aug 8, 2011 by TomE

We have a board based on the MCF5329, but this problem could apply to the MCF5373, MCF5208 and others.

We are using 32-bit SDR (non-DDR) SDRAM on a non-split bus.

Some boards intermittently lock up on power on. They are most sensitive to "long brownouts" where the power is turned off for about one second and then turned on again. Some boards never (seem to, so far) fail, others do sometimes. Sometimes as little as 1 in 200 switch-ons, but that's one time too many.

Checking a wedged board shows the SDRAM is driving data onto the data bus before and after RESET, and this prevents the CPU from fetching code from the FLASH chip, so it crashes and halts.

We've been working with our distributor and Freescale Support for 5 weeks on this and are making good progress in understanding the problem and developing workarounds.

A fast power-on ramp is required to show this problem. Boards powered from a plug-pack turned on at the mains don't do this. Ones switched to existing supplies (battery, bench supply) do. So you may not see problems on the bench, but do get them in the field.

I'd be surprised if we're the only ones seeing this, but not surprised if we're the first ones to be closing in on the root cause.

Has anyone else had reports of problems like these?