The R5F100GD is the 48 KB member of the 48-pin row: 3 KB of RAM, the 4 KB
data flash, ten converter channels and forty-four I/O in the 7 by 7 mm LFQFP
at 0.5 mm pitch, with an HWQFN option. It brings the 48 KB class’s FF300H
self-RAM window into the family’s widest sub-64 KB package, and it is the
member of that class chosen when the I/O count, not the memory, is the
reason for the part.

FF300H in the widest small-memory package

The class maps its 3 KB of volatile memory from FF300H upward, with the
flash library’s workspace at the top of that range. A recovered linker
map that shows the reservation marks an update-capable build, and on
this member the layout can be checked against the live chip through a
0.5 mm fixture. A readout loader settles below the window, in ground
the application was built to leave clear.

Forty-eight blocks, two clusters

The program fills forty-eight erase blocks, four at the bottom forming
the boot region and the next four holding its mirror, with the security
configuration duplicated at 010C0H and 010C4H when the swap feature is
active. The flag in the first block names the live copy, and on
maintained boards the retired one keeps the firmware generation the
unit began with. Both are read on every capture, because their
difference is the update record.

The interrupted write and its signature

Every write lands on a four-byte word between block-level erase and
verify cycles; power lost mid-update stops the pen mid-word, leaving old
and new bits sharing one address. That signature separates a failed
field update from a hardware fault on I/O-heavy boards before deeper
work begins, and the two diagnoses lead to different jobs, the second
of which is the examination flow on the chip reverse engineering service page.

Ten channels and the I/O profile

The converter’s ten inputs and the forty-four I/O give this member its
relay-bank-and-sensor character, calibrated from the 4 KB data flash
with thresholds held in code. The array’s wear-levelled log keeps the
unit’s usage record, and capturing it alongside the code is what makes a
cloned controller drive the original board correctly instead of
approximately.

The security posture

Four option bytes, the debug gate with its erase-on-failure choice, two
ten-byte identifiers and block protections enabled at shipment: the
whole posture fits in the first kilobyte, and none of it gates a read.
The passive capture of that block opens every job here, and the erase
bit’s state sets the terms for the first emulator attempt.

Getting at the part

A 0.5 mm fixture is ordinary work, and when the layout routes nothing,
lift-and-reball onto an adapter is the standard fallback. The
IC decapsulation service route and the firmware extraction service page cover what the bench cannot.

Row context

Within the 48-pin row the neighbours are R5F100GA memory readout, R5F100GC locked flash
and the members from R5F100GE program memory to R5F100GL firmware decryption. The 48 KB die itself recurs as a
24-pin leaded part R5F1007D locked flash, a 30-pin leaded one
R5F100AD code flash extraction, a 25-ball grid R5F1008D embedded memory, a 36-ball grid
R5F100CD firmware decryption, the 40-pin QFN R5F100ED memory dump and the 44-pin LQFP
R5F100FD flash heximal. Service entry points are MCU crack service and IC clone service.

Cohabiting with the application in 3 KB

The 48 KB class maps volatile memory from FF300H with the library’s
reservation at the top, and a readout walker must live below it.
The space is tight but adequate, and the cohabitation rule is
strict: the walker touches nothing the application owns, keeps its
buffers inside its own region and restores the stack it borrows.
Executed properly, an in-circuit capture finishes with the board
running exactly as it was found, counters intact and logs
undisturbed. On industrial boards where the operating-hours record
is contractually significant, that property of the session matters
as much as the capture itself.

The same rule protects the analyst: a session that touches nothing it does not own cannot be blamed for the fault that arrives later, and the boundary between walker and application is where that guarantee lives.