Technical documentation

This document catalogs the **features MegaFlash exposes to the Apple IIc/IIc+**, and how to call them:

**MegaFlash** is an internal storage and I/O card for the **Apple IIc / IIc+**. It plugs into the Memory Expansion slot and is built around a **Raspberry Pi Pico (W)** plus **Winbond NOR flash**, with a **GAL** for address decode. The 65C02 only moves data between its RAM and …

The **firmware** folder contains **Apple IIc / IIc+ system ROM patches**. The IIc has no slot ROM socket; $C100–$CFFF is internal ROM only. MegaFlash therefore **replaces** the built-in “Memory Expansion” (Slinky) firmware in **virtual slot 4** by patching the original ROM and…

This document describes the Uthernet II (W5100) emulation implemented in the MegaFlash firmware. Slot selection uses the **default MegaFlash bus behaviour** (no GPIO slot-select pin); the card responds when the bus is active for its slot.

This document supplements `docs/Implementation-notes-and-reasoning.md` (§1j–§1ak, §1az) with a consolidated **data-path view**, **diagrams**, **function contracts**, and a **prioritized TODO list** with **validation checklists**. Primary sources: `pico/uthernet2.c`, `pico/uthe…

Both the **Uthernet II** (AppleWin emulation) and **MegaFlash** (hardware) use the same Apple II slot I/O region and decode the same **low 2 address bits** for their first four registers. So from the 6502’s point of view, the **first four C0x locations have the same address la…

**Goal:** Make the [ip65](https://github.com/cc65/ip65) TCP/IP stack work with MegaFlash’s Uthernet II (W5100) emulation. **No changes to ip65.** The MegaFlash Uthernet II emulation must satisfy ip65’s expectations.

This document records the thinking, root-cause analysis, design decisions, and dead ends from work on the MegaFlash Pico firmware (Uthernet II, build, GPIO, C0C4 visibility). It is intended for future maintainers and for debugging similar issues.

This document adapts the cc65 MegaFlash library to the **C environment used by A2osX**. It describes:

This library gives cc65 programs (Apple IIc / IIc+) a small, C‑friendly wrapper around the **MegaFlash** `$C0C0` command interface:

Short answer: **not as a direct drop-in**, but **yes in principle** by reusing the **design and protocol ideas** and reimplementing them on MegaFlash’s hardware and software stack.