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PSoC 3
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You can use a zener diode as a noise genertor
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The problem with sampling internal Vref, like the band gap or Vdd,
is that noise has a correlation component to it due to processor
activity. How big that is I do not know.
Consider the PRS, can be up to 64 bits.
Rergards Dana.
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Would the PRS good enough?
However, if people can physicaly access your equipement, then whether you are using external or internal noise generator may not make much a difference.
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I would assume the principal problem you have using A/D
is its finite resolution convolves a less than true random
result on the sampling of noise. That coupled with thermal
noise is not truly random, and noise in a UP environment
has non zero correlation, all lead to a pseudo random, not
true random result.
You could in verilog make a much larger PRS, say 128 bits,
to help. Food for thought.
Regards, Dana.
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The PRS accepts a "Seed" value from which you may generate different sequences from. When you store the actual seed in an EEProm-location at startup, you can generate a new seed out of it which again you save in EEProm for the next startup.
Bob
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In Creator, Start Page, "Find Example Project", there are example
projects for EEPROM and Emulated EEPROM (in FLASH), the former
has longer erase / write cycle lifetime, 1,000,000 cycles 20 year vs
100,000 20 year or less for the latter depending on temp.
Regards, Dana.
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You are always welcome!
Look at datasheet for associated specs tied to lifetime, namely temp.
Regards, Dana.
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You could always use the SPC (die temp sensor) to create a psuedo random seed for the PRS.
The PSoC® 3 devices have an on-chip temperature sensor that is used to measure the internal die temperature. The temperature sensor uses the Delta Vbe method for digital temperature measurement.
The temperature sensor block has an auxiliary analog-to-digital converter (ADC) to measure the internal die temperature. The
auxiliary ADC is a 10-bit accurate ADC in the system performance controller (SPC) primarily designed for measuring temper
ature sensor output. It is also possible to route the analog output of diode in temperature sensor block to analog globals to
measure temperature using the higher resolution Delta-Sigma ADC in PSoC 3.
Or use another PRS to create the seed.
Regards, Dana.
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My error, it is a software only component, so you cannot route
die temp sensor to ADC.
Regards, Dana.