>>>>The changes from Balloon 2 are:
>>>>- VDD_3V is now VDD_IO (still a 3.3V supply)
>>>>- VDD_5V is now VDD_RAW (which is 'rough' 5V)
>>>
>>>Well, sort of. If you feed 5V in, it'll be 5V... If you strap it to a  
>>>lithium cell, it won't be.
>>>Bear in mind that these pins could as easily be used to feed power into  
>>>the balloon, as to feed power from the Balloon to the other board -  
>>>depends if you see the board as a backplane or an expansion card, really.
>>
>>Yes, agreed.
> 
> Umm we use VDD_3V to feed the power in, will this still
> work or is VDD_IO some other supply we make all
> connections to the board though the connector ?

This won't work properly, sadly. VDD_IO is an output from the MAX1586 
switcher for the ARM. Balloon 3 uses a different power supply 
architecture from Balloon 2, where all rails are generated on the board 
from the raw 5V(ish) supply. I think this is necessary because it's the 
way that the ARM (and FPGA, if fitted) expect to have their power 
managed, as far as I can see. It actually simplifies the power 
arrangements, but could be awkward for people used to feeding 3.3V in.

>>DQM3..0 would be much more useful, I agree. Can anyone from Guralp 
>>(James McKenzie?) comment?
> 
> sorry pins 1,3,5,7 ARE DQM0-3 are they not?
> 
> We pass these through to a h3800 connector and are used by
> something which I don't think we'll be making any more of.
> 
> HOWEVER if you drop these - then you commit yourself to
> using only 8 or 16 bit IO. You won't be able to drive a
> chip like the smc lan91c96 in 16 bit mode.

I've changed them to be DQM3..0 on the new pinout, but on Balloon 2 
they're definitely labelled as NCAS3..0 on all the schematics I have. 
Whatever, henceforth they're DQM3..0 because they're much more useful.

>>>>- MBREQ/DREQ<0> and MBGNT/DVAL<0> are present on the Samtec so  
>>>>motherboard devices can do bus mastering and DMA
>>>
>>>I guess I ought to pull these to a safe state on Balloon :)
>>
>>I'm sure we'll be discovering myriads of things like that...
> 
> Sorry are these in or out?

These are on the samtec: MBREQ/DREQ<0> is the input for requesting bus 
mastering/DMA, and MBGNT/DVAL<0> is the output for granting it.

Chris

-- 
Chris Jones - chris@martin-jones.com
Martin-Jones Technology Ltd, makers of Solidlights
148 Catharine Street, Cambridge, CB1 3AR, UK
Phone +44 (0) 1223 474968 Fax +44 (0) 870 112 3908
http://www.solidlights.co.uk/