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).
Antony.