RE: MPC860 CP / CPM Misbehaving

descriptors (BDs) from the CPM with the OV bit set (bit 14 of the RxBD
status/control field, "Overrun. Set when a receiver overrun 
occurs during
reception").

- SDRAM setup. If ORx(BIH)=1 makes the problem go away, your burst setup

or the /TA pullup is broken. NB: Neither the SCC 

nor the SMC do bursts.

I checked my SDRAM setup.  SDRAM is the only device configured with UPMA and
it's on cs1, so I checked UPMA, OR1, BR1, MAMR configuration along with
MCR/MAR process for issuing precharge, refresh, and SDRAM mode register
config per the datasheet for the parts.  This board is a few years old, so I
wasn't able to find the datasheet the original timings were made from -
instead I looked at the datasheet for the parts we're using now, and (since
the parts we're using now are faster) our memory timings are somewhat
conservative.

I did try disabling bursts, with no luck.  Not sure what "NB" means. 

- Did you by accident happen to enable any IDMA lines?

No

- Did you happen to misconfigure RCCR(DRxM)?

RCCR is all zero's except RCCR[ERAM]=b11 since I have the SCC/SMC microcode
patch.  Even though IDMA is disabled, I have tried setting RCCR[DRPQ]=b10 to
make IDMA requests have the lowest priority (didn't help/hurt).  The DRxM
bits are edge sensitive.

- Did you happen to misconfigure the SDCR?

SDCR[FRZ] = 0 (ignore the freeze signal)
SDCR[FAID] = 0 (highest priority default, although I'm not using FEC).
SDCR[RAID] = b01 (priority level 5)

One other thing. If you have an old BDM debugger *and* if the problem

occurs *only* with the BDM debugger hooked up, you may 

want to check for an update or replacement. Old debuggers sometimes used a

method to do BDM which could stall the DMAs in 

the machine and cause this kind of overrun/underrun effect.

Hmm...interesting.  How old?  Does this happen when actively debugging
(setting breakpoints, etc) or just running with no breakpoints set?  I have
two different debuggers, a OCD raven wiggler and a BDM module for my
HP16702A logic analyzer.  I have to run different debugger software on each
for licensing reasons (SingleStep 7.5 on the raven and GHS MULTI4.0.5 on the
HP).  The problem occurs on both.

Heinz