First public commit.

lenser/amiga/copper.py

@@ -0,0 +1,41 @@
+"""Build an Amiga Copper list that displays a static 320x200 low-res screen.
+
+The Copper runs every frame and re-loads the bitplane pointers + registers, so
+the picture stays stable.  Each instruction is a MOVE (register offset, value);
+the list ends with WAIT $FFFF,$FFFE.
+"""
+from __future__ import annotations
+
+import struct
+
+DIWSTRT, DIWSTOP, DDFSTRT, DDFSTOP = 0x08E, 0x090, 0x092, 0x094
+BPLCON0, BPLCON1, BPLCON2 = 0x100, 0x102, 0x104
+BPL1MOD, BPL2MOD = 0x108, 0x10A
+BPLPT = 0x0E0                          # BPL1PTH; +4 per plane
+COLOR0 = 0x180
+
+
+def list_len(nplanes, ncolors) -> int:
+    pairs = 9 + nplanes * 2 + ncolors  # DIW*2, DDF*2, BPLCON0/1/2, BPLMOD*2 = 9
+    return pairs * 4 + 4               # + end WAIT
+
+
+def build(nplanes, ham, plane_addrs, colors) -> bytes:
+    bplcon0 = (nplanes << 12) | (0x0800 if ham else 0) | 0x0200
+    moves = [
+        (DIWSTRT, 0x2C81), (DIWSTOP, 0xF4C1),
+        (DDFSTRT, 0x0038), (DDFSTOP, 0x00D0),
+        (BPLCON0, bplcon0), (BPLCON1, 0x0000), (BPLCON2, 0x0024),
+        (BPL1MOD, 0x0000), (BPL2MOD, 0x0000),
+    ]
+    for p, addr in enumerate(plane_addrs):
+        moves.append((BPLPT + p * 4, (addr >> 16) & 0xFFFF))
+        moves.append((BPLPT + p * 4 + 2, addr & 0xFFFF))
+    for i, c in enumerate(colors):
+        moves.append((COLOR0 + i * 2, c & 0x0FFF))
+
+    out = bytearray()
+    for reg, val in moves:
+        out += struct.pack(">HH", reg & 0x1FE, val & 0xFFFF)
+    out += struct.pack(">HH", 0xFFFF, 0xFFFE)      # end of copper list
+    return bytes(out)