Every RX24T part gives two ways in, and on the 384 KB device the choice between them decides how long the job takes. R5F524TCADFP carries 384 KB of code flash, 32 KB of RAM and the same hundred-pin body as the rest of the group, so the serial programmer path and the on-chip debugger path both exist on the same header. They authenticate against the same sixteen bytes and they react to failure differently, which is the whole story of this density.

Boot mode is a pin, not a menu

The mode pin is sampled while reset is held low and again as it releases. Drive it the wrong way and the device comes up in single-chip mode and runs whatever firmware is in the array, which on a motor board means a live PWM output within milliseconds. Drive it correctly and the same die stops executing user code and waits on SCI channel 1, receive on PD5 and transmit on PD3 in this package, for a host to start a conversation. Nothing in the flash is read until that conversation begins, which is exactly why the erase-on-connect behaviour catches people out.

Twelve volts are not involved and no special programmer is needed: a three-dollar USB-to-serial bridge, a reset line and the mode pin cover it. What the bridge cannot do is guess the ID code, and that is where the job either proceeds or turns into a different kind of job altogether.

The ID code, byte by byte

The record at FFFF FFA0h is one control byte followed by fifteen ID bytes, and both the serial programmer and the debugger read the same copy. The control byte selects what happens when authentication fails: the strictest setting erases the entire array on connection rather than refusing politely, which is the behaviour described in recovering data from a secured part and the reason a first attempt on an unknown board should never be made with a programmer that auto-connects. Blank ID bytes, all FFh, mean no authentication was ever programmed and the part will open for anyone.

There is a second lock behind the first. ROM code protection at FFFF FF9Ch is a single word, and a value of 0000 0000h blocks both reading and rewriting of the user and data areas when a parallel programmer is attached, while 0000 0001h blocks reading only. It can be cleared, but only by erasing block zero in boot mode or through self-programming, and an erase of block zero takes the vector table with it. Anyone hoping to lift the protection and keep the code should stop at that sentence.

Why 384 KB behaves differently from 512 KB

Three hundred and eighty-four kilobytes is 192 blocks of two kilobytes. That is 25 percent fewer blocks than the largest member of the family, and the difference shows up in the verification pass rather than in the read pass. A full read is limited by the serial link, not by the array; a full rewrite is limited by the eight-byte programming unit and lands near two and a half seconds of flash time. Where the first attempt fails halfway, the block map tells you whether the controller stopped at a protection boundary or the link dropped, and those two failure modes look identical on a terminal.

The flash clock has to sit between 1 and 32 MHz with 3.5 percent accuracy for the whole operation. On a bench supply with a long lead this is worth checking before blaming the part, a habit that also pays off on an R5F562TAADFM extraction.

Timing, current and the rest of the die

At 80 MHz the core draws what an inverter control loop expects, and the analog front end is the part that matters afterwards: 22 converter channels on this package, one microsecond per channel, three channels behind a programmable gain amplifier, four comparator channels. The motor timer block gives nine channels and the general PWM timer four. A recovered image is normally checked against those resources first, because a control loop that was written for a different channel count will run but will not regulate.

Serial-programming ID handling on the RL78 side, written up in serial-programming ID handling on the R5F1006A, follows a similar logic with a different record layout, and comparing the two is a quick way to see how much of the RX scheme is vendor convention rather than silicon.

Sign-off

A finished 384 KB job ends with a binary that matches the block map, an ID record captured as bytes, the protection word quoted in the report, and a note stating whether the array was read or reconstructed. Where the answer is reconstructed, the customer is told plainly; a service that promises a read of a protected part is promising something the silicon does not allow. The full sequence, from pin states to checksum, is the same one used in the R5F562N7BDBG lock case on the network-capable RX62N, which is a useful cross-check when a board will not answer at all. Handling for an unfamiliar board, from first power-up to a documented image, is set out in extracting an MCU, and the equipment-level view of the same operation is reading a chip.