Give Z80 a contract before asking for code.

STEP 01

Define a small callable routine

Create a module in Machine Code Studio. Use the actual free origin shown by your project memory map. For this example the routine changes the border to red and returns; it does not modify screen memory or install an interrupt handler.

Generate one SJAsmPlus Z80 module for ZX Spectrum 48K.
Example origin: 32768; entry label: main. I will verify this range is free.
Set border colour 2 through port 254 and return to BASIC with RET.
Preserve IY and the caller stack; declare any other clobbered registers. No interrupt handler, file access, INCLUDE, scripts or external binary data.
Explain the port side effects and calling contract. Do not assemble, run or claim a successful test.

STEP 02

Keep source generation separate from execution

Generate with AI creates editable assembly source. Read it before Assemble. Use F1 on instructions you do not understand and compare the declared clobbers to the actual code. For existing ASM, use contextual Copilot to request a minimal patch instead of regenerating the whole module.

STEP 03

Assemble and inspect placement

Assemble the source with bundled SJAsmPlus. Inspect diagnostics, byte size, symbols and memory collisions. External file reads, scripts and arbitrary outputs are intentionally blocked; do not bypass those guards to make a model-generated module build.

STEP 04

Run the isolated test deliberately

Choose Test Routine. In the 1.6 runner, read simulated time, instruction count and PC. Pause retains CPU and RAM; Continue resumes that state. Stop ends the test as inconclusive. The automatic safety pause after 30 seconds of host execution is not a failed routine or a musical-length limit.

The border routine should return normally with the caller stack intact. A long-running player needs a different expectation than this tiny RET routine.

STEP 05

Accept the binary, then integrate BASIC

Only after review use Accept & Use Binary. Review the generated BASIC integration, including CLEAR, LOAD CODE and RANDOMIZE USR. Build the complete TAP and verify that execution returns to the next BASIC line. An isolated test does not add the routine to tape for you.

STEP 06

State the extra 128K constraints

For a banked module, repeat the actual physical bank, window address and caller paging contract in the request. Do not ask the model to guess a bank from $C000. Review the banked loader and test from the intended caller configuration.

Before editing this 128K routine, list the placement and paging facts you need. Do not assume the current RAM bank from a logical address. Preserve caller paging and stack; do not change project target or accepted CODE placement. Explain which tests would demonstrate the contract, without claiming they have run.