R5F100FC pairs 32 KB of code flash with the 44-pin LQFP, keeping the 2 KB
RAM, 4 KB data flash and the ten converter channels of the row. The 10 by 10
mm body at 0.8 mm pitch is the family’s most serviceable package, and at
this capacity the member is the workhorse of interface and control boards
that need a real program store with a wide analog front end and room for a
relay bank.

Thirty-two blocks and the configuration block

Thirty-two erase blocks carry the program, four at the bottom forming
the boot region with its mirror at 02000H, and the opening kilobyte
collects vectors, option bytes, the identifier pair and the flag,
protected from the factory. Whether the mirrored option bytes at 010C0H
were ever written shows at a glance whether field configuration updates
were planned for this board, a fact that shapes the whole session plan
before the first tool moves.

Ten channels across a wide board

The ten converter channels are the row’s signature, and on this member they
typically carry the full sensor spread of an interface board: two
temperature points, a supply divider, the mains-synchronous pair and a
user-adjustable input. Calibration for all of them lives in the 4 KB data
flash, thresholds in code, and the pair together is what a cloned board
needs to behave like the original. The data array’s wear-levelled log also
records the unit’s usage history.

ROM-resident updates and their traces

With 2 KB of RAM the self-programming library runs from ROM and the
application halts during any flash operation, so updates here are short
and surgical. They leave a trace anyway: the option block’s state and a
counter ticking over in the data array, which dates them without
documentation. An interrupted update leaves a half-converted word at the
boundary it reached, and that signature separates a failed update from a
hardware fault at the first read.

The identifiers and the safe order

The two ten-byte secrets gate the two tools separately, and the
destructive erase bit in the fourth option byte applies to the debug
path. Reads stay open, so block zero is read passively before anything
else happens and the decision of what to connect follows from evidence.
On interface boards the serial secret is usually present and the debug
side varies.

Access at 0.8 mm

The 0.8 mm pitch makes fixtures and lifted-part work equally
straightforward, and the part survives a lift onto an adapter without
drama. The die remains available through the IC decapsulation service route when the
package is not the obstacle but the image is, and the imaging workflow is
on the firmware extraction service page.

Row context

The 44-pin row includes R5F100FA memory readout and runs from R5F100FD flash heximal to
R5F100FL firmware decryption. Elsewhere the 32 KB die appears as the 20-pin
R5F1006C code flash extraction, the 30-pin R5F100AC flash memory, the 32-pin
R5F100BC flash heximal, the 36-ball R5F100CC code flash extraction and the 40-pin
R5F100EC embedded memory. For the protection contrast with a previous generation
that lacked a separate data array, see LPC2101FBD48 processor memory, and the family
index is microcontroller unlock.

Half-configured boards and what they leave open

The two ten-byte identifiers are written by independent decisions, and
production reality produces all four combinations. Both blank is the
open chip. Serial secret only leaves the emulator path. Debug secret
only leaves the boot ROM. Both written is the closed case that pushes
work toward identifier reconstruction or the physical layer. The
destructive bit in the debug option byte complicates one of the four,
which is why the option area is read before the first connection on
every job. On a leaded 0.8 mm part the read is quick, and the ten
minutes it takes routinely decides whether the project is an afternoon
or a week.

The four-state enumeration also explains pricing: three of the four states close in a single session, and only the fully closed case, both secrets written and the destructive bit set, justifies the reconstruction work that follows. Quoting a job before the option area is read is quoting blind, and the ten-minute read is what turns an estimate into a plan.