A bench that handles a hundred different devices will eventually build a fixture from a pinout diagram and trust it. On the 100-lead XMEGA A1 that habit has a specific failure waiting for it, because two adjacent supply pins are not where the rest of the family has trained you to expect them.
Read the Note Under the Diagram
The datasheet’s pinout drawing carries a footnote that is easy to skip: the supply and ground assignments on pins 83 and 84 are reversed relative to the other supply pairs on the same package. The reason given is routing. Putting ground where ground is needed makes the 32 kHz crystal layout cleaner on a dense four-layer board, and the vendor chose that convenience over pinout consistency.
For a product designer this is a minor curiosity. For anyone building a socket, a spring-pin adapter or a probe card, it is the difference between a working fixture and a dead part. A generic 100-lead adapter wired from the family table will feed supply into a ground pin and ground into a supply pin, and the device will not survive the first power-up.
Count the Pins Before Trusting the Drawing
The 256A1 is a 100-lead thin quad flat package with a 0.5 mm pitch and a 14 mm body. It has 78 general-purpose input and output lines, which is a large part of why the family was used for panel controllers and instruments with wide front panels. The exposed centre pad is not optional either: it should be soldered to ground for mechanical stability, and on a fixture it needs its own contact rather than being left floating.
None of that changes between the 64A1 and the 384A1, which all share the 100-lead outline. Only the supply arrangement on that one pair differs, and only on this family. Two checks are worth building into the routine: buzz out the supply pins against the socket before the first insertion, and photograph the adapter with the pin numbers marked so the next job does not repeat the exercise.
What the Part Holds
The 256A1 carries 256 KB of application flash in 512 pages of 512 bytes, an 8 KB boot loader in 16 pages, 4 KB of data EEPROM across 128 pages of 32 bytes, and 16 KB of SRAM. Its identification pattern is 1E 98 46.
The 512-byte page is the family norm above 64 KB, so the addressing split is the same as the 128A1, 192A1 and 384A1. What differs is the count: 512 application pages against 384 on the 192A1. A capture that stops at page 383 returns 192 KB of a 256 KB array and looks complete, which is the quiet failure mode on this density. The last application address is 0x3FFFF, and the boot loader runs from 0x40000 to 0x41FFF.
Where the Physical Work Starts
When the lock fields are programmed, no fixture helps, and the job moves to the package itself. A 100-lead thin quad flat package with a 0.5 mm pitch is a demanding decapsulation target: the leadframe is fine, the mould compound is thin over the die, and the margin for error at the bond pads is small. The semi-invasive route is usually the first choice because it leaves the metal layers intact, and the analysis report that comes with it documents what was found, which is often as valuable to the customer as the image itself.
Parts that have been in service for fifteen years bring their own problems. Conformal coating, potting and corrosion all change the preparation, and a board that has been running hot will have a die attach that separates during thinning. The damaged chip FAQ covers how much of that is recoverable, and the honest answer is that it depends on which failure happened first.
Package the Result Properly
A 256 KB read is not a single file to email. Deliver the application array, the 8 KB boot loader, the 4 KB of EEPROM and the fuse and lock state as separate items, each with its own checksum, plus two independent reads compared byte for byte. The user signature row is worth capturing at the same time: it is one page of flash that survives a chip erase, so on a refurbished or salvaged part it may still hold the previous owner’s serial number or calibration constants, and nothing will recover it later.
Booking the Work
Send the full top marking, the package type, the board function and the quantity. State whether the part is known to be locked or whether that is still unknown, since the answer changes the plan from a bench read to a laboratory job with a different schedule.
The services overview lists what each route includes, and a short description of the board with a photograph of the device in place is enough for the engineering desk to confirm the package and the likely path before anything ships.