boot up issues

[neil]

Hi Mark
  I have been using utasker on my MC52259 boards for years and most of the time it works no problem.  I am using a fundamental 48 mhz crystal (ABM7-48.000MHZ-D2Y-F-T ) 18pf with  load  capacitors both being 33pf, and a 1M parallel resistor. Both CLCKMOD[1,0] pins are 0v, with XTAL=3.3v (through a pullup) . Occaionally I cant even program some boards . So I tried setting CLCKMOD[1,0] to 3.3v and leave off pullup with XTAL connection. This programs and if I run this , then it works fine, but if I try to debug the application the line
 MCF_CLOCK_SYNCR = ((((PLL_MUL - 4)/2) << 12) | CLKSRC | PLLMODE | PLLEN | (POST_DIVIDE << ); // set up PLL to generate the required frequency 
causes an illegal command error from cpu.  Any idea why this would happen?

Best Regards
Neil

[mark]

Hi Neil

I haven't experienced this behavior but also haven't work with the Coldifire devices for a long time.

If you experience problems with an access to a register I would switch the debugger to disassemble mode and watch the way that it prepares the value to be written and also the instruction that it uses for the write. It may be that it crashes "just after" the write due to the fact that it has causes something to be out of specification (clock).

If you skip individual instructions you can see whether subsequent lines still run and thus home in onto the exact instruction that fails.

Hard faults on register writes are mainly due to the module not being enabled but if the module can't be disabled (always on) check also the power pins that supply the module to ensure that they are all well connected.

Since this sounds to not be a general problem but restricted to certain boards you may find something that is "just out" of specification or a certain HW error just on these boards.

Regards

Mark