5445x Bus Monitor

[cmaryan]

Is it possible to get an exception out of the bus monitor on the MCF54454?

I'm trying to track down what I believe is a bad Flex Bus access, one that causes the bus to hang. Presumably it's to an address that's not mapped to a CS.

If the bus monitor is disabled, but the core watchdog is set to interrupt-then-reset mode, I don't get the interrupt (because the bus cycle never completes; if I got the interrupt, it would give me a stack dump which would help).

If I turn on the bus monitor, it seems that the bus monitor terminates the bus transaction, doesn't throw a fault, and lets the CPU go on it's merry way. Which isn't particularly helpful.

Is there a way to get the bus monitor to throw an exception? Failing that, is there a way to configure the flex bus to throw an exception when you access FB space that isn't mapped to a CS? Anyone else find the documentaton of the bus monitor a little lacking?

Thanks

Chris

[ChrisJohns]

Who has the bus ?

The bus error monitor will assert the TEA (or what ever) signal but it a DMA engine has the bus then that hardware will have to record the fault and you will need to check that device.

[cmaryan]

Never mind, the bus monitor fault just wasn't obvious (that is, the register that enables the exception for the bus monitor isn't obviously associated with the bus monitor).

For others trying to solve similar problems, the register that controls the bus monitor exception is the CFEI bit of CFIER and SCMISR. Also note that the bus monitor is enabled by default in the 54454, but does not throw an exception by default. That means that the default behaviour of the CPU is that a bus error will allow the CPU to go on its merry way, despite getting bad data from the flex bus. With whatever consequences that entails for your particular application.

Chris

[aersek]

We are using bus monitor on MCF5282 processor, it is configured to 1024 cycles in CCR register and we get ACCESS ERROR trap on wrong access. It operates regulary on our project.

Best regards

Andrija