Will CompactFlash work with 3v?

Do you mean 3, or 3.3? All standard-compliant CF cards are specified to work at 3.3 or 5V.

as well as the motherboard.

only if the host system is 3.3V compliant. There is no guarantee to be so for IDE interface.

Anyway, the OP has 3V power (even for 3.3V power), which would not be sufficient to drive 5V logics and questionable for 3.3V logic.

Huh? What are you talking about? The question is, "will a CF card work with 5V supply". The answer is, that the CompactFlash specification requires all CF cards to be capable of operation with either 3.3V or 5V on the power rails. I don't understand your posting.

If he has only 3.3V power, then how could his board be using 5V logic levels?

I think he's saying that there are motherboards that won't work with

3.3V, and having a CompactFlash working at 3.3V is irrelevant if the IDE controller on the motherboard won't.

--
Alex Pavloff - remove BLAH to email
Software Engineer, ESA Technology

AFAIK, the signalling is all TTL levels, so if the CF (powered by 3V3) is driving signals to the motherboard then there isn't a problem there. But the signals going from the motherboard to the CF could cause the system to fail if the CF doesn't like voltage levels higher than 3.3V. If the CF had 5V tolerant inputs then AFAIK there shouldn't be a problem.

I have never had the need to investigate whether there is anyone who makes

5V tolerant CF, so I don't know if such a device exists.

Regards,

Paul.

---------- Remove _rem_ before replying by email.

I apologize for causing the confusion. I was just thinking about the specific case for one of our client using the IDE-CF adaptor (similar to the pcengine adaptor except for the power adaptor). In this case, our client was very concern about uncontrolled power loss on the CF. So they provide a separate power line to the CF to be controlled by the main system. They regulated the 12V (rather than using the 5V) system supply and shut down at about 4V. This is to be sure of valid logic level for the 5V system.

Actually, if the CF is powered by 3V3, then there would be a problem driving 5V logic on the motherboard.

The CF adapter is for an embedded project (not going into a PC). I know a CF card will work with 5v and 3.3v, but my situation is such that the databus is 3.3v but my power supply to CF adapter is only 3v. So all I was wondering was if the CF would work with only 3 volts power applied to it.

The answer is YES! That worked fine.

The only problem is, that its a 4MB card formatted with FAT12 and the code Ive inherited is for FAT16. I bought a USB CF Card reader so that Windows XP/DOS could format it, but it also formats it to FAT12. Is there any way to force a 4MB (currently FAT12) CF to FAT16. I now its not as efficient, but it would make things much easier for development.

Ben

You can just copy a fat16 file template into the CF. We have an empty template at

Since it was partitioned differently from DOS, it would not be usable for DOS. However, it works for Linux and might work for you. We custom partition the CF because DOS wasted 25% (one cylinder out of 4) of the CF space.