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MicroBlocks
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Posted: 27 April 2016 at 5:26pm | IP Logged Quote MicroBlocks

Thanks Peter!

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Grogster
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Posted: 28 April 2016 at 8:56am | IP Logged Quote Grogster

Yeah, the datasheet does not specify if those pins need pull-ups.
At the moment, I am treating them like EEPROM chips and assuming they have internal pull-ups, meaning that WP can be left floating, and just pulled down to deck to enable WP mode.

My chips arrived today, so I will try to get one hooked up to test.

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Posted: 28 April 2016 at 9:12am | IP Logged Quote MicroBlocks

This is how i wired them in the schematic.


If you could do a little test that would be great as i don't have the parts yet.



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Posted: 28 April 2016 at 9:26am | IP Logged Quote piclover

MicroBlocks wrote:
This is how i wired them in the schematic.


If you could do a little test that would be great as i don't have the parts yet.



I don't see why you use a pull up on ~HOLD and ~WP: these could be tied up directly to Vcc.

On the other hand, there should be a pullup resistor on ~CS, so that on power on and before the Micromite pins are properly configured (and thus the CS pin properly driven), there is no risk of spurious writes to the flash chip, due to floating pins.
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MicroBlocks
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Posted: 28 April 2016 at 9:54am | IP Logged Quote MicroBlocks

Peters configuration was with a pullup on both ~HOLD and ~WP. The datasheet does not specify if a pullup is needed or if it can be tied to Vdd directly, hence my question as the only way to find out is to test it.

The snippet from the schematic has to be changed to work correctly.
I agree about the pullup on the ~CS, i not like floating pins at all. It could be however that that pin has an internal pullup. Back to the datasheet again.....


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Posted: 28 April 2016 at 10:05am | IP Logged Quote matherp

Quote:
At the moment, I am treating them like EEPROM chips and assuming they have internal pull-ups, meaning that WP can be left floating, and just pulled down to deck to enable WP mode.


I'm pretty certain when I was doing the development I tried this and it didn't work - a proper external pullup was needed, either resistor or tied to VDD.

Quote:
I don't see why you use a pull up on ~HOLD and ~WP: these could be tied up directly to Vcc.


Agreed: I just think it is good practice to always use a resistor - just protects the chip and makes it easier to connect a uP pin at a later date

Quote:
On the other hand, there should be a pullup resistor on ~CS, so that on power on and before the Micromite pins are properly configured (and thus the CS pin properly driven), there is no risk of spurious writes to the flash chip, due to floating pins.


Agreed
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Posted: 28 April 2016 at 11:05am | IP Logged Quote MicroBlocks

Ok, i have updated the schematics.
The datasheet does not mention an internal pullup on the ~CS pin.




Edited by MicroBlocks on 28 April 2016 at 11:10am


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Posted: 28 April 2016 at 11:52am | IP Logged Quote Grogster

...the bloody datasheet does not mention the requirements for pull-ups at all on any pins, and it is something that really should be there in the PDF. The fact it was missing, made me think that it must therefore have internal pull-ups, and you don't need to worry about them. If it was important, they would have written about that in the datasheet.

False logic?

Perhaps.....

I use jumpers or solder-blob pads to pull WP to deck(ground) on the I2C EEPROM type chips pretty much as standard design, so that you can choose between writeable and write-protected modes easily later, and this concept requires pull-ups rather then direct connection to supply(or you would short out the supply), unless this is documented and allowed for in the PDF(device has internal pull-ups kind of thing).

Again, if the datasheet was to have been kind enough to have enlightened us on that aspect of the device, that would have been nice.

My design will therefore use three 10k pull-ups: WP, HOLD and CS.
I have space, but I realise this is not quite for you, MB.

@ matherp - did you have pull-ups on the data lines, or just WP, CS and HOLD?

Edited by Grogster on 28 April 2016 at 12:02pm


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Posted: 28 April 2016 at 12:45pm | IP Logged Quote MicroBlocks

There is one hint in the datasheet:
WARNING: if the /WP or /HOLD pins are tied directly to the power supply or ground during standard SPI or DUAL SPI operation, the QE bit should never be set to a 1.
The QE bit stands for 'Quad Enable'.
If that bit is set then the /WP and /HOLD pin will be IO pins that can cause a short.

That is settled then. Use a pullup resistor on each one of them.
Bummer, now i have to find some more space......




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Posted: 28 April 2016 at 12:52pm | IP Logged Quote Grogster

Nice find, buddy.

What a cryptic way of saying: 'Suitable pull-up resistors should be used on WP, HOLD and CS pins."

You can get those tiny resistor arrays in 1206 or even 0805 - usually four resistors in one, the size of the 1206 or 0805 package. That is an option for you if you are really squeezed for space.

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Posted: 28 April 2016 at 1:03pm | IP Logged Quote MicroBlocks

Now to squeeze in those two resistors.
Not much room to play with.



I will have a look at those arrayss.
I need five resistors. two for the I2C pullup, and three for the winbond chip.
It might be possible as i can move the I2C pullups to another area of the PCB.
Oh boy, this is going to be some rework....


Edited by MicroBlocks on 28 April 2016 at 1:05pm


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Posted: 28 April 2016 at 1:14pm | IP Logged Quote Grogster

Just in case you don't know what I am getting at:

0805 resistor array, 10k x 4

The total size is 0805, made up out of 4x 0402 10k resistors - VERY tiny.

The link above is an example only - one euro per 0805 + postage is a bit rich for my blood.....

EDIT: Element14 actually have them MUCH cheaper then the eBay price, which is not something often said.

Element14 10x x 4 0805 SMD resistor array

4c each in our NZ dollars, MOQ of 150 pcs, so six bucks in my money for 150 arrays.

Your local Element14 probably uses the same part number, if you wanted to try them.

Edited by Grogster on 28 April 2016 at 1:22pm


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