Chip off and JTAG…

Chip off and JTAG is the process of removing a memory chip from a circuit board and reading it. This applies to solid state drive and mobile phone data recovery. The chips are programmed with ‘JTAG’ or Joint Test Action Group and acronym for the group that set the standards for testing integrated circuits. However chip off techniques are not as simple as they might seem. The data recovery engineer needs a familiarity with all the proprietary configurations, memory types and JTAG connectors for a data recovery to even remotely be successful.

A knowledge of repair, dismantling and chip removal, together with reassembly and imaging are what we teach our engineers in the laboratory. NAND memory, NOR memory, volatile RAM FTL and wear levelling are all essential subjects which the engineer must master.

Chip removal is the practice of de-soldering the chip from the circuit board, often using a microscope. It is a risky business and without proper care and handling, will result in data loss. JTAG is less risky and does not jeopardise the data. Here we simply probe the test access ports. JTAG is our preferred option, but is often not as successful as chip off techniques.

Once the chip is off, the next step is to read the memory. TSOP NAND chips are relatively straight forward due to the standardisation of the format. These are found in memory sticks, SD cards and iPhones 3G. Other chips can have multiple connectors on the underside which are secured with epoxy. BGA (Ball Grid Array) chip construction does not have a common standard and every chip can be different making it much more difficult for our data recovery engineers.

Reading the memory is done with special hardware that can accommodate most TSOP pin configurations. BGA configurations on the other hand are much more problematic. Manufacturers all configure their chips differently. Add to this varying levels of encryption and reading these chips becomes much more difficult. In most cases we expect to create an image of the hex data and manually carve through this to rebuild the files. Sometimes we already have custom scripts to automate this process.

Chip off and JTAG give us the best data recovery yield rates and are opening up new avenues of data recovery techniques. Our research team are kept constantly busy trying to stay one step ahead as technology is constantly evolving.