CFD fuse location for 328PB?

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The datasheet is unclear about the fuse required for clock failure detection on the ATMega328PB.

 

The only mention anywhere of the fuse is in 13.2, which refers to “FEB” bit 4. I don’t know from FEB, but EFB is the Extended Fuse Byte (Table 33-4). However, this table is unchanged from the 328P datasheet. Bit 4 is undefined.

 

AT15007 doesn't talk about fuse changes at all.

 

So what changed in the fuses between the 328P and 328PB? In particular, Is EFB bit 4 the CFD enable fuse?

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Clock Failure Detection (CFD) is discussed in Section 2.2 of AT1507. Thats a new one to me, and, frankly, a welcome one. It is discussed in Chapter 13 of the full manual. But, you seem to be right about the fuse attribution. Like you, I came to the conclusion that "FEB" should really be "EFB" but the fuse map (Table 33-4) shows nothing. The indicated "Bit 4" is an un-assigned bit in that table. I guess that I would try it, with the understanding that it MIGHT be wrong and that you could "brick" the chip :-( Please tell us if you do try!

 

Its a long time coming and one that MSP430s have had since almost day-one.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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It's not as fully-featured as I'd like. Frankly, I don't know why they didn't just change it so that the chip used *exclusively* the 128kbit internal clock during serial programming - that is, ignore the clock bits when !RESET is pulled low and force the 128kbit clock. That way programming would always succeed (as long as !RESET wasn't disabled) regardless of the clock configuration. It would slow serial programming down, certainly, but it'd be a small price to pay.

 

I'm really asking about it so I can make sure that the appropriate fuse is *not* programmed. :D

Last Edited: Sun. Sep 4, 2016 - 10:04 PM
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Bit 4 is wrong. CFD fuse can be found at bit 3. (0x08)

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Bit 3 of the Extended Fuse Byte?

 

That would make sense, as that's the first unused bit.

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Yes - bit 3 of the Extended fuse byte. The bug is already logged and will hopefully be published soon...