Default output levels of I/O pins at reset - MCS9S12E256

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Default output levels of I/O pins at reset - MCS9S12E256

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blood
Contributor III
I have noticed while debugging a different issue that the output level of I/O pins is different when the micro comes out of reset. The micro I am using is a MCS9S12E256.
Out of reset I noticed Port M pin 3 goes low while pins 4, 5 and 6 went high. These pins are being used as general I/O pins so they all have the identical circuitry attached to them and therefore I was expected the output level on them to be the same when coming out of reset.
The only explanation I could come up with was because they have different secondary functionality. Can any one confirm if that is expected.
 
 
 
 
 
Added p/n to subject.


Message Edited by NLFSJ on 2008-07-08 02:32 PM
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kef
Specialist I
If you look at table entitled "signal properties", you'll find that PM4-PM7 pull-ups are enabled out of reset, while PM3 pull-up is disabled out of reset. However PERM register rescription states all pull PORT M pullups should be off out of reset. Something's not right here. If "signal properties" is right, then PERM should read 0xF0 out of reset...
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blood
Contributor III
Thanks for that.
I hadn't looked at the signal properties chapter.
I also checked the register at startup with a debugger and the PERM register definatly has 0xF0 in it.
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