some newbie questions

Ed Sutter els at
Thu Feb 19 19:33:40 UTC 2004

I just did a quick scan of the 68360 user's manual...

The CONFIG2–CONFIG0 pins select the QUICC initial configuration during reset (see Table
2-6). They decide whether the CPU32+ core will be enabled or disabled, the global chip
select port will be 8-, 16-, or 32-bits, and the MBAR address will be $003FF00 or
$0033FF04. After reset, these pins may be programmed to their other function. The
CONFIG2–CONFIG0 lines have internal pullup resistors so that if they are left floating, the
default selection will be 111. See Section 6 System Integration Module (SIM60) for more

Are you sure you're using the right MBAR address?  According to the above text,
the MBAR will be at 0x3ff00 or 0x33FF04.  Looks like you may be off by 0x300000.


sebastian ssmoller wrote:
> hi,
> finally i used the approach: incrementing a variable an see where it
> stops.
> > Seb,
> > Just reset the board (don't powercycle).  In most cases this doesn't
> > corrupt memory.  Usually, assuming you have a reset or NMI type
> > of button, you can get yourself back to the monitor, then in RAM
> > space you essentially have the equivalent of a core dump.
> i did so and it worked perfectly well.
> i started debugging at c/src/lib/libbsp/m68k/gen68360/start/start.S
> where the start symbol which i call is defined. i found out that the
> board hangs immediately at step 4 where mbar is set.
>   /*
>    * Step 4: Write the MBAR
>    */
>     movec   dfc,d1          | Save destination register
>     moveq   #7,d0           | CPU-space funcction code
>     movec   d0,dfc          | Set destination function code register
>     movel   #m360+0x101,d0  | MBAR value (mask CPU space accesses)
> /* with the execution of the next line the board will hang */
>     movesl  d0,0x3FF04     | Set MBAR
>     movec   d1,dfc          | Restore destination register
> the original addr of the MBAR was 0x3ff00 as described in the 68360
> manual (which failed). i read again the doc of my board and it says that
> MBAR is at 0x3ff04. so i changed the value but nothing happens - the
> board still hangs :(
> thx
> regards,
> seb
> (...)--
> Microsoft: Where do you want to go today?
> Linux: Where do you want to go tomorrow?
> FreeBSD: Are you guys coming or what?
> OpenBSD: Hey guys you left some holes out there!

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