68300

Hello everyone,
 
All of the configuration pins on the MC68332 are Data Bus pins.  One of these pins controls port E and another controls port F.  
 
If Data Bus 8 is held high at the release of reset, Port E will be bus control signals, i.e., R/W, SIZ, DSACK, etc.
 
If Data Bus 8 is held low at the release of reset, Port E will be inputs.
 
IIf Data Bus 8 is held high, it is obvious that some of the Port E pins are going to be outputs.  So, grounding (or connecting to 5 volts) one of these pins is going to cause some serious current flow.  Now, you can use a suitable pull-up or pull-down resistor.  However, I think that tying the pin directly to a pwer rail is going to cause problems.
 
On the SIM, Port E is in a High-Z state while reset is asserted.  So, it is the time between the release of reset and when you configure the port that is a problem.
 
 
To answer your question directly, if you hold Data Bus 8 high at the release of reset, Port E will be bus control signals and grounding Port E bit 6 is going to cause problems.  These will probably long term reliability issues.  Recall that some emulation equipment uses the SIZ pins.  If you mess around with Port E and the emulator needs these signals, you will have trouble.
 
Regards,
 
Charlie

-----Original Message-----
From: Rod.Niner@... [mailto:Rod.Niner@...]
Sent: Tuesday, July 15, 2003 10:03 AM
To: 68300@yahoogroups.com
Subject: [68300] PE6


On the 68332, Port E bit 6 has an alternate function of SIZ 0.   I seem to 
remember issues with using this pin regarding startup. It will function as 
Siz0 until we change PEPAR if Data8 is high.  So holding it low during 
this startup could be detrimental? 


Rod Niner
GSE Scales
42860 Nine Mile Road
Novi, MI 48375-4122
ph: 248.596.3350
rod.niner@...

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