+++ Chris Jones [05-06-22 11:13 +0100]:

-------forwarded mail from James McKenzie-------------
> 
> Steve Wiseman wrote:
> >>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 ?

> >We don't need nSDCAS<0..3> (pins 1, 3, 5, 7)
> >They make no sense on the backplane. (rummage. They should be DQM<0..3>)
> SDRAM-related signals, but NCAS0/1/3 don't feature on the (slightly 
> ambiguous) list of things that Guralp definitely aren't using, so I 
> didn't meddle with them. It's hard to see what they'd be using them for, 
> anyway.
> 
> 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.

> 
> >>- 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?

James.




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