Is there any way to use two flash chips ?

nikki81

New Member

• May 14, 2017

• #1

I have just been thinking if there is any way to use 2 flash chips on a tp-link td-w8970 one with the stock firmware and one with openwrt on and a switch to select between them. I have found this circuit diagram will it work ?

**broken link removed**

Nikki x

 

P

Pommie

Well-Known Member

Most Helpful Member

• May 14, 2017

• #2

It should work in theory. However, in practice it will only work when the device is switched off. In fact, if you happen to switch when a write is taking place you could mess up one or both chips.

Mike.

 

Mikebits

Well-Known Member

• May 14, 2017

• #3

Check out 1 to 2 decoder chips. I am sure you can find the right logic. The Diode will cause a violation to the flash VIH spec.

 

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Pommie

Well-Known Member

Most Helpful Member

• May 14, 2017

• #4

The minimum input high voltage is VCC x 0.7 = 2.1V. The forward voltage drop of that diode at 1.5mA is around 0.2V. Shouldn't be a problem.

Edit, I'd be more worried about it being switched when on. Is the /WP pin tied low?

Mike.

 

Mikebits

Well-Known Member

• May 14, 2017

• #5

I just assumed the standard .7v drop. I suppose from the diode data sheet the spec is ok. They do have single 1 to 2 decoder IC's which would be much less parts.

 

Mikebits

Well-Known Member

• May 14, 2017

• #6

Pommie said:

Edit, I'd be more worried about it being switched when on. Is the /WP pin tied low?

Click to expand...

I would change the switch to a jumper plug.

 

nikki81

New Member

• May 15, 2017

• #7

thank you. I think I need to get my breadboard out and do some experimenting. Using a jumper plug is a good idea !

Thanks Nikki