JMicron SATA controllers

[Art]

Hi Guys,
If you have an external USB Dual SATA Dock,
an external USB to SATA/IDE adapter,
or a USB HDD enclosure that is internally SATA,
there's a very good chance it's driven with a JMicron chip.

It might be a good exercise for a beginner to sink their teeth into
(or someone who has been away for a while :D),
to rewrite the configuration on the I2C EEPROM chip.
The EEPROM contains the USB vendor string that displays in Windows
Device Manager,
as well as configuration options set my manufacturer that are usually out of
our hands, such as whether the device looks to connect to SATA devices, or USB first.

Here is an example EEPROM layout (end of the data sheet) for external SATA USB 2.0 adapter:
http://www.scribd.com/doc/162287233/JM20339-datasheet-V2-3-061012

I can confirm that my Dual SATA dock (USB 2.0) has a JMicron chip with
SATA port multiplier, and has the EEPROM chip with information as well.

The USB vendor string appears to have an EEPROM location for it's length byte so watch that.

[Ioannis]

Sorry, but I missed the purpose of this exercise.

Ioannis

[Art]

For beginner to read and write entire EEPROM in a loop with I2C,
Change configuration settings that can not normally be accessed.

For me (USB Dual SATA Dock), I wanted to turn off the port multiplier
so it could boot from either HDD port, but also in that mode,
only one drive can be mounted at a time.

The problem that was resolved is,
two dual boot computers with three different op systems that
do not all agree with each other's file systems.
I wanted to turn drives off individually (to prevent them going nuts)
depending on the op system being run currently,
but without having to pull the drives out physically all the time.
There are many possible configurations achieved by either pulling pins,
or changing EEPROM locations.