A disassembly makes claims about what a program does, and some of those claims can be checked against the hardware without understanding the program at all. The most useful of those checks is the pin count.

Every peripheral channel on a microcontroller ends at a pin, and a pin exists only if the package bonds it. A design in a large package can drive eight timer outputs; the same die in a small package can drive three, and the firmware written for the large one will contain configuration code for channels that have nowhere to go. Reading a disassembly against the package turns a plausible narrative into a checked one.

R5F562T7DDFK#V1 is an RX62T group device in the largest of the package fields this group offers. The version suffix identifies a shipping configuration; the memory class and the group name the silicon; the package field is what this page is about.

Where the pin count bites

The third row is the subtle one. Peripherals exist on the die regardless of package, so the firmware’s initialisation code will configure them, and only the pin multiplexing tells you whether they go anywhere. A design that initialised four serial ports on a part that bonds two is a design written for a larger sibling — which is either a bug or a deliberate multi-variant firmware.

Using it as a check

The check is mechanical and it takes minutes.

List the peripherals the disassembly claims, by looking at the configuration sequence at the start of the code. Then list the peripherals the package can actually reach, from the pin assignment table. Compare.

Three outcomes are informative.

Everything claimed is bonded. The analysis is consistent with the hardware, and the confidence in the rest of the listing goes up.

Something claimed is not bonded. Either the firmware is multi-variant, or the listing is wrong, or the die is a different member than assumed. All three are worth knowing before delivery.

Something bonded is never configured. This is the most interesting outcome, because it means the design has a feature the code does not use — an unused channel, a test point, a connector that was removed in a later revision. It is also the outcome that catches a truncated read, because a listing that stops early will show unconfigured peripherals that the design clearly needed.

The multi-variant problem

Products that ship in several hardware variants frequently share one firmware image, with the variant selected at run time by a strapping option, a stored parameter, or the state of an input.

For a recovery this creates an identification problem that has nothing to do with the code. The image is the union of several behaviours, and the unit in hand is running one of them. Which one is decided by data, not by code, so the interesting question moves to the parameter area.

That is also why a customer asking for “the firmware from this unit” may be asking for something slightly different from what a read returns: they want the firmware and the variant selection, and only the second explains the behaviour they observed.

What the bonded pins say about a fault

There is a practical use for this analysis beyond verification.

When a unit fails in the field, the pins that are bonded and driven are the ones that can have failed electrically, and the ones that are bonded and floating are the ones that can have picked up noise. A listing that shows a channel being driven tells a technician where to put a scope.

On a motor-control part the useful case is concrete: the timer outputs that drive the bridge are a small, known set, and a listing identifies exactly which compare channels produce them. That converts a schematic-reading exercise into a five-minute lookup.

Reporting the peripheral map

The artefact worth producing is a table: peripheral, channel, pin, whether the package bonds it, and whether the firmware configures it. Four columns that answer the question “what can this code actually affect”.

That table is what a maintenance engineer needs before changing anything, and it is what a failure analyst needs before attaching a probe. It is also the most reusable part of a recovery, because it does not depend on the revision of the code — it depends on the design.

For the ordering fields that determine the package in the first place, R5F562T6ADFK software decodes them. For what the body costs once it has to be opened, R5F562TAEDFM heximal covers access. And for the configuration bytes that decide which peripherals start enabled, R5F562TABDFF program covers the option area.

FAQ

Can absent pins still be configured? Yes. The peripheral exists on the die and accepts configuration regardless of whether the pin is bonded. The configuration simply has no external effect.

Does a larger package mean more firmware? It usually means more configuration code, because more channels are initialised. It does not necessarily mean more functionality.

Is the pin count enough to identify the variant? No, but it narrows the possibilities, and combined with the parameter area it usually settles the question.

The short version

The package is a constraint on the firmware, and constraints make good checks. List what the code configures, list what the pins can reach, and compare — a mismatch means multi-variant firmware, a wrong assumption about the device, or a truncated read. Then report the peripheral map, because it is the part of the recovery that stays useful after the code has been forgotten.

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