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I'm trying to understand this table, which specifies the operating ranges for a dataflash memory I am trying to use.

The one part that I don't understand is where it says Fr under conditions. What does that mean? Why are there two numbers? Can that be measured by a multimeter?

The datasheet is here.

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    \$\begingroup\$ Can I get a link to the datasheet? \$\endgroup\$ – AndrejaKo Mar 16 '11 at 0:53
  • \$\begingroup\$ Alright, I posted a link to it. \$\endgroup\$ – 200ok404notfound Mar 16 '11 at 0:57
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Fr and fr are described on page 36 of the datasheet. They are the clock frequencies the data bus is running at. Basically, at the lower rate (33 MHz), the chip can tolerate slightly lower voltages (down to 2.7V), but at the higher rate (50MHz), it needs to be above 3.0V.

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  • \$\begingroup\$ Is that the same thing as the SPI frequency? \$\endgroup\$ – 200ok404notfound Mar 16 '11 at 1:37
  • \$\begingroup\$ Yes. It's the clock frequency for the SPI signal. \$\endgroup\$ – anthony137 Mar 16 '11 at 1:45
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I'd recommend that you read the entire datasheet few times, as it seems that information is scattered around the datasheet.

For your question, Fr and fr are two different things.

Fr is

Clock frequency, for fast Read (0Bh) and all other instructions except Read Data (03h)

fr is

Clock freq. Read data instruction 03h
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