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MPC5675K: Machine check exception from EBI

Question asked by Sean Donohue on Apr 22, 2014
Latest reply on Jul 7, 2016 by Laura Yindra

Hi, I am trying to determine the cause of an intermittent machine check exception from the EBI controller when performing a read. The EBI is used to communicated with an external SRAM device. I can single step through my code all day and never see a machine check exception when I do reads. If I run at full speed, I will get a machine check after reading the same address 15-100 times; it varies. The exception will also occur when reading any random address within the address space of my 256KB SRAM device. The exception occurs on an se_lhz instruction (specifically: se_lhz r31, 0 (r3), where r3 is 0x20540000). MCSR is 0x0008800C, indicating the exception occurs on a load instruction, but strangely the BUS_WRERR is also set. MCSRR1 is 0x00008000 which is different than the run-time value of MSR, 0x0200A000. I do have the bus monitor enabled and configured for ~1us timeout; the longest a transaction can take from the SRAM device is 800ns. So even if the exception is caused by a bus timeout, should I just get an EBI timeout flag and not an exception?

 

Here are the rest of my EBI settings:

MCR: 0x06000005

BMCR: 0x00000580

BR0: 0x200008a7

OR0: 0xE0000000

 

Thanks,

Sean

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