ata interface newer drive voltages

[Terradestroyer]

Are newer ATA 6 compatible hard drives running their interface at 5v or
3.3v.

I'm working on a mircocontroller interface and I think that older hard
drives 5v lines caused damage to my not 5v tolerant device (I thought
it was, better check datasheets next time). But what is strange is that
the ata5 drive I have seems to only output 3.3v over the ata interface,
so is it safe to figure that never drives only need to deal in 3.3 or
do i need to be able to select 3.3v or 5v in my interface for different
modes.

Thanx in advance
Keith

 

[Arno Wagner]

Are newer ATA 6 compatible hard drives running their interface at 5v or
3.3v.

I'm working on a mircocontroller interface and I think that older hard
drives 5v lines caused damage to my not 5v tolerant device (I thought
it was, better check datasheets next time). But what is strange is that
the ata5 drive I have seems to only output 3.3v over the ata interface,
so is it safe to figure that never drives only need to deal in 3.3 or
do i need to be able to select 3.3v or 5v in my interface for different
modes.

Since 3.3V can be made to give correct logic levels, tis could well
be unstandardised. I don't have the standard, since it costs money.
But a look into the last freely available draft of the T13 comitee
on ATA-6 says that V_IH may be in the 2.0...5.5V range and V_OH
needs to be at least 2.4V. These are standard TTL levels and can
well be supplied by modern CMOS wuth a 3.3V supply. My guess
is that the HDD uses 3.3V logic.

Bottom line: Get 5V tolerant interface chips, unless you want to
measure this for each HDD individually. Also note that the
HDD and controller are required by the standard to tolerate up
to 5.5V input voltage.

Arno

Reference: http://www.t13.org/project/d1410r3b-ATA-ATAPI-6.pdf, page 11

 

[Terradestroyer]

Thank you for the information. I'm hoping to get more specifics on the
exact hard drive i'm planning on using from the manufacturer so i might
still be able to get away with my current 3.3v chip, but I am
considering switching to another one that is 5v tolerant. This will
likely reduce all my problems.

Currently working with a WD 800jb drive. If anyone knows the specifics
of its interface voltage, would apperciate it.

Thanks
Keith