Pico 2 Memory Map Explorer
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About This MicroSim
"Memory-mapped register" is one of those phrases that stays abstract until you can point at where it lives. This diagram gives the Pico 2's address space a shape: three labeled bands you can click, with the register block broken out into the four sub-blocks this course actually uses.
The bands are not drawn to scale — flash is far larger than the register block in reality. What matters here is the classification, not the proportion.
The key distinction the sim is built around: flash and RAM are storage. An address in either one names a cell that holds a value you put there. A memory-mapped register address names no cell at all — it is wired straight to hardware, so reading it samples whatever that hardware is doing right now. That is why reading a timer register twice gives two different answers while reading a RAM address twice gives the same answer.
How to Use
- Hover over each band to get a one-line summary before committing to a click.
- Click Flash, then RAM, and compare the "volatile" lines. Which one survives unplugging the board?
- Click into the register sub-blocks. Notice that none of them are labeled volatile or non-volatile — ask yourself why that question does not apply.
- Press each code snippet button in turn. Each one jumps the "you are here"
marker to the region that snippet actually reads, and explains the connection:
gc.mem_free()→ RAMmachine.unique_id()→ the Unique Device ID registeropen("main.py")→ flash
- Press Reset to return to the default view.
Controls
| Control | Purpose |
|---|---|
| Click any band or sub-block | Opens the full definition, an example, and volatility |
| Hover any band | One-line summary tooltip |
gc.mem_free() |
Highlights RAM |
machine.unique_id() |
Highlights the Unique Device ID register |
open("main.py") |
Highlights flash |
| Reset | Returns to the default RAM selection |
Lesson Plan
Grade Level
Undergraduate (college junior/senior)
Duration
10 minutes
Prerequisites
- Variables live somewhere in memory
- A program is stored as a file before it runs
Learning Objective
Students will be able to classify a given address or piece of data as belonging to flash, RAM, or the memory-mapped register block, and explain why reading a register address behaves differently from reading ordinary RAM.
Activities
- Sort the items (4 min): The instructor names items — a sample buffer, a saved WAV file, the current GPIO pin state, the firmware itself. Students classify each into a band and defend the choice.
- Snippet trace (3 min): Students press each code button and write down which region it reads and why.
- The reread question (3 min): Students explain why calling
machine.unique_id()twice returns the same value but reading a timer register twice does not, even though both are register reads.
Assessment
Ask: "You unplug the board and plug it back in. Which of the three bands still holds what it held before? Which is now empty? Which question does not apply to the third band, and why?"
Related Resources
References
- RP2350 Datasheet — the authoritative address map and peripheral register listings for the Pico 2.
- Memory-mapped I/O — the general technique of exposing hardware through the address space.