piclist 2003\01\31\033316a >
Thread: Pin won't turn off properly
www.piclist.com/techref/ubicom/devices.htm?key=sx
face picon face BY : Jinx email (remove spam text)



> I still think you are seeing a read-modify-write issue. Have
> you tried 2 nops between the setb and clrb?

(Thanks for the reply)

Yes, as noted in the OP. Also tried 1000 - no change. The only
thing that works is in the post you replied to. Sometime over the
weekend I'll make a couple of PCBs with different layouts and
also see if the problem exists at frequencies other than 50MHz.
I have to get to the bottom of this before I can move on to other
code

> It's possible that port a has some slightly longer propogation
> delays that may explain it's different results from other ports

I can't comment as I don't see that parameter in the data.However,
the phenomenon still doesn't make sense to me. It's <spock> highly
illogical </spock>

> Also, what type load is being driven? I high capacitive load (long
> traces?) could explain this behaviour.

2" PCB traces (32mil) to a header connector. Either a 5mA resistive
load, no load or CMOS gate inputs. Any SX o/p pin is rated to drive
45mA, so I don't think that's the problem

> The PORTRD bit was added in the SX48/52 to help combat this
> behaviour

I'm not even sure what behaviour this is

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Subject (change) Pin won't turn off properly

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