R5F100BE brings 64 KB of code flash and 4 KB of RAM to the 5 by 5 mm 32-pin
HWQFN, with the 4 KB data flash of the small-memory row and eight converter
channels. At this capacity the part crosses the threshold where the flash
self-programming library runs from volatile memory, and the family’s whole
in-field update machinery becomes available inside a package still small
enough to hide under a thumb. The recovery-relevant facts are the same
protection architecture as every sibling plus a memory map that has room to
work in.

The FEF00H window

On the 64 KB members the volatile memory maps to FEF00H through FFEFFH, and
the flash library reserves its self-RAM window from FEF00H upward. A linker
map that shows the reservation identifies a firmware built for field updates
and tells the analyst exactly where a readout loader belongs. During erase
and write the sequencer stops serving code fetch from the array, so anything
that must keep running while the flash is busy has to live in that window or
alongside it, and on this part the budget fits both comfortably.

Sixty-four blocks with the swap option

The array splits into sixty-four one-kilobyte blocks, four of which form the
boot cluster and four more at 02000H form the swap target. At 64 KB the swap
cost is six percent, so the feature is common, and both clusters carry
duplicated option bytes and ten-byte identifiers at 010C0H and 010C4H. A
board that has been updated in the field holds its previous firmware in the
inactive cluster, and the boot flag in block 0 says which generation is
running. The standard capture takes both clusters, the flag and the option
block.

DTC versus DMA in the update path

The family provides a two-channel DMA controller and a data transfer
controller, and update routines use them differently: DMA moves blocks
between the communication buffer and RAM while the sequencer works, and the
DTC serves the single-byte transaction choreography that the serial protocol
needs. In a recovered image the choice is visible in the interrupt structure,
and it matters for any repair because the update path’s timing margins depend
on which controller carries the load.

Identifiers and the safe order of work

The ten-byte debug ID at 000C4H to 000CDH and the ten-byte serial ID at
000CEH to 000D7H are independent gates, and the destructive bit in 000C3H
applies to the debug path. The safe sequence is unchanged across the family:
read block 0 passively, determine both identifier states and the option byte
configuration, and only then decide which connection to make. On boards of
this capacity the serial identifier is usually populated and the debug side
varies, which makes the passive read the highest-value fifteen minutes of the
job.

The data flash and the QFN bench

The 4 KB data flash holds calibration and wear-levelled logs in its own
blocks with their own flags. It is read with the data-flash command set and
captured alongside the code array. Physically, the 0.5 mm wings and bonded
pad set the access route: layout features first, lift-and-reball second, and
the die through IC decapsulation service last. The single-wire TOOL0 pad remains the pin
worth finding on any layout of this package.

Row context

The 32-pin siblings are in R5F100BA locked flash through R5F100BD program memory and up to
R5F100BG flash data. The 64 KB die in leaded packages is the 30-pin
R5F100AE firmware decryption, the 20-pin R5F1006E firmware decryption and the 24-pin R5F1007E flash heximal.
Architecture contrast with a family whose 64 KB part had no separate data
array and a different block discipline is in LPC2134FBD64 mcu flash memory, and service-level
entry points are the firmware extraction service and microcontroller unlock service pages.

The flag byte and its inversion

The boot flag occupies a fixed spot in the first erase block, and the flash
library inverts it to select the other cluster at the end of a successful
update. Because the flag shares its erase block with the vectors and the
security bytes, inverting it re-erases a kilobyte that contains everything
the chip needs to start, which is why the library sequences the operation
carefully and why an interrupted inversion is recoverable but never
silent. A capture that includes the flag raw, before any interpretation,
lets the analyst replay exactly which copy the reset logic selected on the
last power-up of the unit.