Atmel T89C51CC01 PSEN pin, bootloader

From: Paul Smith (ptsmith_at_nospam.indiana.edu)
Date: 01/24/04 

Date: Sat, 24 Jan 2004 05:59:17 GMT

Part data *** and CAN bootloader documentation recommend "releasing"
PSEN before the end of RESET when using PSEN=0 as the "hardware
condition" forcing the on chip CAN bootloader to execute.

The Atmel Demo board just has a DIP switch to ground to force PSEN=0; it
  doesn't "release". Even though the Demo board doesn't use PSEN as an
output, shorting this pin to ground must not be a good idea.

Does anyone have a practical circuit to properly drive and release the
PSEN pin? The data *** is pretty vague about the properties of this
pin during the brief time it is an input. How about grounding it
through a resistor? value?

Can the on-chip CAN bootloader be used to boot more than one T89C51CC01
on a CAN segment? If not, what is the best way to boot/ISP a bunch of
these parts on the same CAN bus segment? They will all get identical
code loaded into them.

TIA!!

Paul Smith
Indiana University Physics

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