[E3-hacking] PBL V5.1

Antony Stone Antony.Stone at e3.open.source.it
Wed Oct 10 12:34:06 BST 2007

On Wednesday 10 October 2007 12:14, David Given wrote:

> Neil Stainton wrote:
> > Sorry if this has been covered before, but can't the NOR flash be read
> > or rewritten simply by bit banging the memory bus via JTAG? The JTAG
> > port on the POMAP5910JGDY is IEEE 1149 compliant which I take to mean
> > that all the I/O on the device can be manually overidden.
> >
> > Is the JTAG port brought out to a handy set of pads somewhere? If not,
> > are the appropriate balls brought out to vias underneath the CPU?
> Yup, this is perfectly possible, and I believe that there are some handy
> pads inside. (If you brick the device this is the only way of fixing it.)
> However, in order to reflash it, you have to take the lid off, do some
> soldering, and apply some technical knowledge --- which means that it's
> not going to be suitable for mass production. Reflashing using PBL,
> though, only requires plugging a jack in the back of the machine.

Yes, but considering that (as far as I know) we've never seen a retail unit 
already containing PBL 5.1 (this only happens when the machine gets poisoned 
by plugging it into a UK phone line), it means that:

 - anyone who wants to reprogram virgin devices en masse can do so using the 
jack socket on the back, talking to PBL 4.9

 - anyone who wants to rejuvenate a used device which has been "upgraded" to 
5.1 can do so with the once-off inconvenience of using the JTAG socket/pads

I'm assuming of course that it's possible to reflash 4.9 into a device using 
the JTAG interface, although I've never attempted to do this (I've made sure 
none of my E3s get near a phone socket).


I want to build a machine that will be proud of me.

 - Danny Hillis, creator of The Connection Machine

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