Hi,
with SPI you should use inidvidual /CS signals to select different devices.
Klaus
General rule:Then leave the /CS pin of the rest of the flash chips unconnected.
Hi,
General rule:
Never leave any (unused) input floating.
Now the question is: is the /CS pin pulled up? Or is it floating?
Klaus
Either internally or externally. You just need to prevent it from floating.You mean internally? I am not sure here is the datasheet
Hi,
Either internally or externally. You just need to prevent it from floating.
If pullup is not mentioned in the datasheet...then most probably there is no internal pullup.
Klaus
nCS isn't pulled up internally, you need to provide external pull-up resistors for unconnected nCS pins.
The schematic in post #1 drives the SPI signals by 5V logic. I don't expect that AT45DB081 has 5V tolerant inputs.
/CS = high effectively disables any input or output to the IC. It is active low, that's what the '/' tells you so to disable it the pin has to be pulled high to VDD. The remaining pins can stay connected as they are. Use a pull-up resistor on both /CS pins so no matter which is disconnected by the jumper is disabled. The resistance isn't critical, I would suggest 10K would be adequate as the /CS pin draws negligible current and the ATMEGA should be capable of sinking several mA.
I really wouldn't use that LED voltage dropper though, it is asking for problems, especially as the current drawn by the flash will vary quite a lot depending on whether it is reading, writing or idle. it isn't only the supply pin that should be 3.3V, the control signals should be 3.3V as well.
Brian.
Noble simplicity! "It works" is an observation of limited significance. May be now but not next time. You should check if the chip allows the control signal to swing higher than Vdd + 0.6V or has built-in clamp diodes. In the latter case, Vdd will probably rise above safe limit of 3.6V.It must have, because it works. This is not my schematic.
I should have wirtten: "In my eyes J7 in your schematic of post #12 does not disable..."In my eyes J7 does not disable the FLASH, it just disconnects the pullup. This is the wrong way.
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