R5F100EC pairs 32 KB of code flash with the 6 by 6 mm 40-pin HWQFN, keeping
the 2 KB RAM, 4 KB data flash and the nine-channel converter of the row. The
combination of a mid-sized image, a large I/O count and nine analog inputs
makes it a common landing for heating and ventilation controllers, and its
bench character is set by the QFN: 0.5 mm wings, a bonded centre pad, and
access that depends entirely on what the layout exposes.

Thirty-two blocks and the configuration block

Thirty-two erase blocks carry the program, four forming the boot region
and four more the mirror at 02000H, and the first block gathers the
vectors, the option bytes, both ten-byte identifiers and the flag into
one kilobyte. Protection, including the boot-area guard, is active from
the factory, so even a chip nobody configured resists an accidental
rewrite of its most critical kilobyte.

ROM-resident updates and what they leave behind

With 2 KB of RAM the self-programming library runs from ROM, halting the
application while the sequencer works. Field updates on this member are
therefore short and surgical, usually one or two blocks, and they leave a
recognisable trace: the option block’s last-modified state and a counter
in the data array advanced once per session. Reading those traces
alongside the arrays dates the updates without any documentary evidence
at all.

Nine channels and the control law

The converter’s nine inputs carry the sensing that a ventilation or heating
loop needs, typically including the mains-synchronous pair the appliance
safety standard expects. Thresholds are constants in code; calibration and
the fault log are records in the 4 KB data flash. The two arrays together
explain how the board behaved, and a recovery that captures only code
produces a controller with the right instructions and none of its memory.
Threshold drift with temperature is the classic hidden fault on such
boards, and the calibration history in the array shows whether it was
ever compensated.

The identifiers and the safe opening

The two ten-byte secrets work independently: one for the emulator, one
for the TOOL0 programmer, with the erase bit in the fourth option byte
applying to the debug path. Because reads need no authentication, block
zero is captured passively first, and the bytes decide whether a debugger
connection would be refused, permitted or self-destructive before anyone
tries one.

Access on the 6 by 6 QFN

The larger body leaves more fixture clearance than the 5 by 5 mm row, and
boards with routed test pads make the first connection quick. Where nothing
is routed, the lift-and-reball route onto an adapter is routine and
reversible. The die remains reachable through the IC decapsulation service service when
the electrical routes are closed, and the imaging workflow is on the
firmware extraction service page.

Row context

The 40-pin siblings are in R5F100EA program memory and R5F100ED memory dump through
R5F100EH firmware decryption. The 32 KB die in leaded packages is the 20-pin
R5F1006C code flash extraction and the 30-pin R5F100AC flash memory; in the QFN rows the 32-pin
R5F100BC flash heximal and the 36-ball R5F100CC code flash extraction. Architecture contrast with a
previous generation whose 32 KB class shipped without any separate data
array is in LPC2101FBD48 processor memory, and the family index is microcontroller unlock.

Factory states and what they reveal

Every member of the family leaves the line with boot-area rewrite
protection enabled and both ten-byte identifiers blank. Everything else,
the watchdog policy, the detector threshold, the oscillator choice, the
debug gate, is the firmware author’s decision, made once and written into
the first erase block. That produces a small, enumerable set of states,
and each state implies a different opening: blank identifiers mean the
boot ROM will talk; a written serial secret with a blank debug one means
the emulator is the route; the destructive bit set changes the calculus
of every connection attempt. Enumerating the state from the first
kilobyte is the first act of any disciplined job on this member.
The enumeration takes minutes on a leaded 40-pin part and pays for
itself: each state maps to a documented opening, and the opening
chosen first is usually the last one needed. Boards that arrive
after a failed do-it-yourself attempt break the pattern, and the
breakage itself is recorded as part of the session.