R5F100GK is the 384 KB member of the 48-pin row: 24 KB of RAM, the 8 KB
data flash, ten converter channels and forty-four I/O in the 7 by 7 mm
LFQFP at 0.5 mm pitch. It carries every structural feature of the top
of the line one step down: banked code, a two-copy update zone, the
doubled data array and the protection architecture that ships enabled
everywhere.

Three hundred eighty-four blocks

The code array divides into three hundred eighty-four one-kilobyte blocks
with the boot cluster in the first four and the swap target at 02000H. A
full per-block verification is the acceptance test of any capture, and the
checksums turn a marginal contact into a localised failure. The capture
streams through 0.5 mm leads in seconds, and the hard part of the job on
this member is never the imaging but the interpretation of a segmented,
field-updated image.

Twenty-four KB of RAM and the library

Twenty-four kilobytes run the library, the updater and a genuine
communication stack together, and the reservation at the top of the
space marks an update-capable build. Both boot copies are populated on
maintained boards, the flag in the first block names the live one, and
the banked image above is rebuilt with its windows intact or not at
all.

The update zone and the previous generation

The duplicated option bytes and identifiers at 010C0H and 010C4H travel
with the clusters, and a field update rewrites one copy, inverts the
flag and leaves the retired generation standing beside it. On boards
maintained for years the two copies plus the wear counters in the data
array amount to a complete maintenance log, which is frequently the
missing context
behind a fault report.

The 8 KB data flash

Fault histories, calibration revisions and usage counters sit in the
separate store under wear levelling, reached with the data-flash command
set and guarded by flags of their own. Here the array amounts to the
unit’s biography; a rebuild without it hands the controller its
instructions but no record of what it regulates.

Protection and the passive opening

The gateable surface is small and sits early: option bytes, the debug
decision with its wipe-on-failure bit, two ten-byte secrets, block
protections. Reads stay open, so the passive capture of that kilobyte
comes first, and the erase bit’s state sets the terms of the first
emulator attempt.

Access and the bench

Fixtures at 0.5 mm, adapters, lifts measured in minutes and a part that
returns to service: the physical side is settled early. Escalation, when
it happens, runs from the IC decapsulation service route through the firmware extraction service page to
the chip reverse engineering service flow.

Row context

The 48-pin siblings are in R5F100GA memory readout through R5F100GJ flash memory and
R5F100GL firmware decryption. The 384 KB die in the 44-pin package is R5F100FK code flash extraction,
and the top of the family’s memory range in that row is the 512 KB member
R5F100FL firmware decryption.

Calibration tables sized for six windows

Firmware at this capacity keeps its constant tables where the banked
windows give them room: motor curves, compensation ladders and
temperature maps that smaller members have to compress or approximate.
Those tables are exactly the content a rebuilt controller must inherit,
and they live in the code array rather than the data store, which
changes where a capture’s value concentrates. The six 64 KB windows are
walked and checksummed like any other blocks, but their contents are
compared across firmware generations more often than they are patched,
because stable tables are the best anchors a segmented image offers.

The 24 KB of volatile memory hosts the library, the update protocol and
the communication stack together, and the manifest discipline of the
capture, one checksum per block plus the option, flag and data-array
records, makes any later session comparable with the first. The 8 KB
data store adds the run history under its own command set, and the
48-pin leaded body keeps every physical step of the session ordinary.

Field history at this capacity is unusually rich: both boot copies, the
diff between them and the log array together reconstruct years of
maintenance, and a rebuilt unit inherits that history rather than
starting clean. The 0.5 mm pitch fixture work and the family-standard
session order keep the cost of gathering it low.