[psas-software] JTAG on the MPC5200 thoughts to discuss this evening

Andrew Greenberg andrew at uad.com
Tue Nov 15 13:17:07 PST 2005


>Technically, we don't need the JTAG layout of the MPC5200 in order to
>make use of the onboard flash.

We actually *do* need to know the JTAG path of the MPC5200 because the 
flash chip does not have a JTAG interface (it's just a simple parallel 
flash chip).

The way we program the flash is that we use the JTAG interface to take 
direct control of the MPC5200's pins. We then manually toggle the bus pins 
on the MPC5200 to send parallel commands to the flash. That's why it's so 
very, very slow. For every word we sent out to the flash, we have to toggle 
through the whole JTAG chain in order to load that word onto the output 
pins of the processor.

Ugly, but true.

Andrew



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    Andrew Greenberg - andrew at uad.com - 503.788.1343
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