Commit 74e755aa authored by Alexandre Kaspar's avatar Alexandre Kaspar

Take aways

parent 15939bed
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......@@ -335,21 +335,30 @@ In our program above, we're using `1110`, which we can understand by looking at
<img src="images/att44_cksel.png" width="400">
We're in the last row case (`111` external crystal or resonator), which means we need to go look farther at page 27:
We're in the last row case (`CKSEL3..0` is within `1000`-`1111` cases, for external crystal or resonator), which means we need to go look farther (at page 27):
<img src="images/att44_cksel2.png" width="500">
And there we find that we're assuming an external crystal/resonator, with frequency from 8MHz and above.
And there we find that we're assuming an external crystal/resonator, with frequency from 8MHz and above (`CKSEL3..1` is `111`).
The last bit `CKSEL0` requires looking a bit further:
<img src="images/att44_cksel3.png" width="400">
Since we have `CKSEL0=0`, it means we assume a ceramic resonator.
Given the additional `SUT1..0=01` (3rd and 4th bits from the left in `01011110`, we know that we have BOD (**B**rown-**o**ut **D**etector) enabled.
Given the additional `SUT1..0` as `01` (3rd and 4th bits from the left in `0101_1110`, we know that we have BOD (**B**rown-**o**ut **D**etector) enabled.
You can read about that [there](https://microchipdeveloper.com/8avr:bod).
The `CKSEL` fuses are the fuses you are the most likely to every change, whereas the other ones are typically very specific.
### Take-aways
1. Read the manuals
2. Read the datasheet (when you need it, no need to memorize)
3. Choose your fuses carefully, notably beware of
* `RSTDISBL` in the *Fuse High Byte*, since this prevent further programming (needed in FabTinyISP), or similar disable / enable options
* Choose the clock carefully and especially the meaning hidden behind each bit's value (e.g. ceramic vs crystal, frequency range ...)
</xmp>
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