First public commit.

lenser/a5200/viewer/assemble.py

@@ -0,0 +1,131 @@
+"""Assemble the Atari 5200 viewer with `xa` and lay out the 32K cartridge.
+
+The cartridge fills $4000-$BFFF.  The 5200 BIOS jumps to the address at $BFFE-F
+(duplicated at $BFE8-9, with $BFFC=0 / $BFFD=$FF) -- verified in MAME a5200.
+
+ANTIC DMAs the bitmap and display list straight from cartridge ROM, so we only
+place them at fixed cart addresses and point ANTIC at them:
+    $4000  viewer code
+    $4100  GTIA register script (offset, value pairs, $FF-terminated)
+    $4200  display list  (ANTIC reads it here)
+    $6000  bitmap        (the converter's 4K-split blob -> $6000 / $7000)
+"""
+
+from __future__ import annotations
+
+import os
+import shutil
+import subprocess
+import tempfile
+
+VIEWER_DIR = os.path.dirname(os.path.abspath(__file__))
+
+CART_BASE = 0x4000
+CART_SIZE = 0x8000
+SCRIPT_ADDR = 0x4100
+DLIST_ADDR = 0x4200
+BITMAP_ADDR = 0x6000          # 4K-aligned: blob $4000/$5000 -> $6000/$7000
+SPLIT_LINE = 102              # matches atari _common.split_screen
+LINES = 192
+
+# ANTIC mode byte + GTIA register script per display mode.  Script entries are
+# (GTIA offset from $C000, colour value); colours come from the converter blob.
+ANTIC_MODE = {"gr15": 0x0E, "gr8": 0x0F, "gr9": 0x0F}
+
+WAIT_MODES = {"forever": 0, "key": 1, "seconds": 2}
+
+
+def _gtia_script(mode: str, colors) -> bytes:
+    c = list(colors)
+    if mode == "gr15":              # 4 colours: COLBK, COLPF0, COLPF1, COLPF2
+        regs = [(0x1A, c[0]), (0x16, c[1]), (0x17, c[2]), (0x18, c[3]), (0x1B, 0x00)]
+    elif mode == "gr8":             # 2 colours: background (COLPF2+COLBK), fg (COLPF1)
+        regs = [(0x18, c[0]), (0x1A, c[0]), (0x17, c[1]), (0x1B, 0x00)]
+    else:                           # gr9: hue in COLBK, GTIA mode 9 via PRIOR
+        regs = [(0x1A, c[0]), (0x1B, 0x40)]
+    out = bytearray()
+    for off, val in regs:
+        out += bytes([off & 0xFF, val & 0xFF])
+    out.append(0xFF)                # terminator
+    return bytes(out)
+
+
+def _dlist(mode: str) -> bytes:
+    m = ANTIC_MODE[mode]
+    dl = bytearray([0x70, 0x70, 0x70])                      # 24 blank scan lines
+    dl += bytes([0x40 | m, 0x00, 0x60])                     # LMS -> $6000
+    dl += bytes([m] * (SPLIT_LINE - 1))                     # 102 lines from $6000
+    dl += bytes([0x40 | m, 0x00, 0x70])                     # LMS -> $7000
+    dl += bytes([m] * (LINES - SPLIT_LINE - 1))             # 90 lines from $7000
+    dl += bytes([0x41, DLIST_ADDR & 0xFF, DLIST_ADDR >> 8])  # JVB -> dlist (loop)
+    return bytes(dl)
+
+
+class AssemblerError(RuntimeError):
+    pass
+
+
+def have_xa() -> bool:
+    return shutil.which("xa") is not None
+
+
+def _assemble(display: str = "forever", seconds: int = 0,
+              video: str = "ntsc") -> bytes:
+    if not have_xa():
+        raise AssemblerError("The 'xa' (xa65) assembler was not found on PATH.\n"
+                             "Install it with:  sudo apt install xa65")
+    waitmode = WAIT_MODES.get(display, 0)
+    rate = 50 if video == "pal" else 60
+    wrapper = (f"#define SCRIPT ${SCRIPT_ADDR:04X}\n"
+               f"#define DLIST ${DLIST_ADDR:04X}\n"
+               f"#define WAITMODE {waitmode}\n"
+               f"#define WAITSECS {max(1, int(seconds))}\n"
+               f"#define RATE {rate}\n"
+               '#include "viewer.s"\n')
+    with tempfile.TemporaryDirectory() as td:
+        out = os.path.join(td, "v.bin")
+        fd, wrap = tempfile.mkstemp(suffix=".s", prefix="_wrap_", dir=VIEWER_DIR)
+        try:
+            with os.fdopen(fd, "w") as f:
+                f.write(wrapper)
+            proc = subprocess.run(["xa", "-o", out, os.path.basename(wrap)],
+                                  capture_output=True, text=True, cwd=VIEWER_DIR)
+            if proc.returncode != 0:
+                raise AssemblerError(f"xa failed:\n{proc.stdout}{proc.stderr}")
+            with open(out, "rb") as f:
+                return f.read()
+        finally:
+            os.unlink(wrap)
+
+
+def build_cart(mode: str, data: bytes, display: str = "forever",
+               seconds: int = 0, video: str = "ntsc") -> bytes:
+    """data = the atari converter blob (bitmap 4K-split at offset 0/0x1000, colour
+    register bytes from offset 0x2000)."""
+    if mode not in ANTIC_MODE:
+        raise ValueError(f"unsupported 5200 mode {mode}")
+    code = _assemble(display, seconds, video)
+    bitmap = data[:0x2000]
+    colors = data[0x2000:]
+    script = _gtia_script(mode, colors)
+    dlist = _dlist(mode)
+
+    rom = bytearray(b"\xff" * CART_SIZE)
+    def place(addr, blob):
+        off = addr - CART_BASE
+        rom[off:off + len(blob)] = blob
+    place(CART_BASE, code)
+    place(SCRIPT_ADDR, script)
+    place(DLIST_ADDR, dlist)
+    place(BITMAP_ADDR, bitmap)
+
+    # cartridge header (verified in MAME a5200)
+    def put16(addr, val):
+        off = addr - CART_BASE
+        rom[off] = val & 0xFF
+        rom[off + 1] = (val >> 8) & 0xFF
+    put16(0xBFFE, CART_BASE)        # start address -- BIOS jumps here
+    put16(0xBFE8, CART_BASE)        # duplicate (validation)
+    rom[0xBFFC - CART_BASE] = 0x00
+    rom[0xBFFD - CART_BASE] = 0xFF
+    return bytes(rom)