MPC5675K: Machine check exception from EBI

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MPC5675K: Machine check exception from EBI

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seandonohue
Contributor II

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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laurayindra
Contributor I

Looking back at my SVN log, I think I have this issue occurring  consistently.

There is 96KB of ramtest SRAM at 0x40021A00, and this error only occurs after a march12 memory test on ramtest.

The error is reading from the EBI, which results in an IVOR1trap

MCSR is 0x0008800C

BUS_WRERR is also set

MCSSR0 is  the last of the following:

    e_lis           r8,0x30000

    e_add16i   r3,r8,0x1408

    se_lwz       r3,0x0(r3)

    se_lhz        r31,0x4(r3)

MCSRR1 is 0x00008000

Here are the rest of my EBI settings:

MCR: 0x06000004

BMCR: 0x00001980

BR0: 0x20000827

OR0: 0xFFB00000

Why does this IVOR1trap only happen after the test on ramtest SRAM?  I don't understand how reading and writing to SRAM is changing the behavior of the EBI bus read.

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davidtosenovjan
NXP TechSupport
NXP TechSupport

Could you specify used SRAM device?

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