[E3-hacking] JTAG/Anyone got a broken E3?

Mike Mnemonic mnemonic at onetel.net
Thu May 4 23:35:42 BST 2006


Matt,
    There is another way. I have previously attempted XRAY with limited
results. I'll look at what I got to see if there is any correlation with
your results.

Regards

Mike Mnemonic

----- Original Message ----- 
From: "Matt Callow" <mc-lists at tesco.net>
To: "Discussion of the Amstrad E3 emailer hardware/software"
<e3-hacking at earth.li>
Sent: Thursday, May 04, 2006 11:03 AM
Subject: [E3-hacking] JTAG/Anyone got a broken E3?


> I've been trying to find the JTAG pins on the E3 again (with limited
> success).  I'm pretty sure I've found TDI and TDO and I can probably
> find nTRST (if it's connected) but finding TCK and TMS is proving more
> difficult.
>
> TDI and TDO appear as 2 of the 8 pads labeled R40 (see
> http://mcallow.pwp.blueyonder.co.uk/e3/img_1986.jpg).
> I found these by using a multimeter to test connectivity between the
> board pads and the CPU  pins. This is possible with TDI, TDO and
> possibly nTRST because they appear at the edge of the CPU BGA (i.e. U17,
> U16 and U15) and I was able to poke a very thin piece of wire between
> the CPU and the board to make contact to those pins, one at a time.
>
> But TMS and TCK are not at the edge of the BGA, so the same method can't
> be used to find them. It would seem sensible to assume that they appear
> as more of the 8 pads labeled R40, but I've found that 3 appear to be
> connected to Vss, 1 to Vdd and the other 2 are connected together!
>
> So, I've been looking on the web at how other people find JTAG pins and
> it seems that one way is to remove the CPU with a heat gun and then
> trace the PCB that way (at least that's the way it was found for the
> NSLU2). So, this brings me to the topic of my post: Does anyone have a
> broken E3 that they could remove the CPU from and trace the board?
> I know it seems like a brutal approach, but It's probably the most
> reliable unless anyone else has any better ideas?
>
> Matt
>
>
>
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