I've been using a 328 which I had switched up to use an external 20Mhz xtal, no problem with that change.
Then I moved the project to a atmega 1284 PU (not 1284P PU).
Doc says max speed 20 Mhz.
Changed the div8 to get to 8 Mhz, no issue.
Then tried to change to the 20Mhz xtal as I need 115.2K serial speed, 8 is too slow for that.
The options were a little different than the 328 -
I set the clk option (I use a Atmel-ICE programmer) to - EXTOSC_8MHX_XX_16KCK_65MS, to get the longest start up time.
Should this be correct? I'm using the same 2 pin crystal with two 22pf caps that I used on the 328.
Wanted to figure out what I have wrong before I destroy another one.
The low byte is FF all unprogrammed - this is what I got from a fuse calculator online for 1284P (didn't list a 1284 - no P) and from the list in the ICE -
The Atmel ICE also said the part was a 1284 and not a 1284P - (but I can't find any differences between them online)
EXTXtal - which I used for the 328, wasn't listed, so I used EXTOSC.
Can I hook some other type of clock up (and how) to recover this chip? I have 8 and 16 4 pin can oscillators and other xtals.
At this point I'm not sure what it is expecting.
Or do I need to buy the 1284P?