Mail Archives: geda-user/2012/04/05/07:39:48
On 04/05/12 06:16, Peter Stuge wrote:
> Peter Stuge wrote:
>> It's a mux on the CS/ line of two SPI flash chips.
>
> Oliver, I really think you should add a real mux to the PCB, and have
> that be "remote controlled" by the jumper or mechanical switch.
Why is that recommended? If using a jumper cap, it shouldn't be able to
go wrong? Chip1 active, none active, chip2 active? To which I can't
understand why that extra component would help.
Not that I don't believe you :p I know nothing of this stuff, but the
goal was to make this board as simple as possible.
>
> It's a small board but I think it can be done. The design I used on
I think it would make the board a little bigger again, or actually the
SOIC8 3306 could fit on top between the connector, so I think it may be
possible using the same size :) Dunno if routing will be still possible :p
> the M57SLI (see http://stuge.se/m57sli/ if curious) is shown in the
Now the left schematic is what your motherboard does? The top right is
what's the smallest component count and the ride side is with an easier
switch, but higher component count?
> attachment, but I suggest to make some improvements:
>
> 1. change things around so that the switch common is GND
> 2. look for little logic to reduce component count
>
> The attachment has two suggested circuits using little logic, one
> with only two components (3306+resistorpack) but which then requires
> a SPDT switch, and one with three components (3306+1g14+resistorpack)
> but which only requires shorting a jumper to ground to switch between
> flash chips.
Even though I am sure that the 3306 method would be better, I don't
understand quite how and why it's needed. Also I haven't found a 3306 on
any of my pcb's to scavenge one off :) I'd reccon the simpler design
would allow for easier adaption?
Finally, I notice you use 100k resistorpacks, but in a previous message
I recall you mentioning anything between 1k and 10k should be good? (I
happen to have a 103 resistor pack on a pcb here is my wondering :)
>
>
> //Peter
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