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schrepta
Observer
Observer
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Registered: ‎11-20-2013

Voltage level translation for Master SPI serial flash

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Using Knitex 7, Master SPI Serial mode. The Serial flash data pins: MOSI, DIN, are listed as bidirectional in UG470.  I need to translate these (and the other) IO voltages from 2.5V to 1.8V for the serial flash.  Can I use uni-directional voltage translators (obviously pointing in the proper direstions), or do these data signals need to be bidirectional?

Also, FYI, the serial flash will be programmed vie the JTAG port. Banks 0, 14, 15 VCCO is 2.5V, serial flash is 1.8V. CFGBVS is at VCCO.  Thanks.

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gszakacs
Instructor
Instructor
4,273 Views
Registered: ‎08-14-2007

As far as I know, these signals are unidirectional if you use x1 configuration (bit serial).  Once you start to use x2 or x4 fast modes, then the flash's data input pin (MOSI) becomes an output.  For x4 mode the write protect and hold pins are also outputs.

 

By the way, if you're using a voltage translator anyway, you might consider using a standard 3V SPI flash since they're generally more available and run faster.

-- Gabor

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gszakacs
Instructor
Instructor
4,274 Views
Registered: ‎08-14-2007

As far as I know, these signals are unidirectional if you use x1 configuration (bit serial).  Once you start to use x2 or x4 fast modes, then the flash's data input pin (MOSI) becomes an output.  For x4 mode the write protect and hold pins are also outputs.

 

By the way, if you're using a voltage translator anyway, you might consider using a standard 3V SPI flash since they're generally more available and run faster.

-- Gabor

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schrepta
Observer
Observer
3,436 Views
Registered: ‎11-20-2013

Yes, I am using a x1, bit serial, flash configuration.

Thank you.

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