JV80/JV880 internal rom extractor

Extract/descramble_internal_rom.py

@@ -0,0 +1,86 @@
+def descramble_data8(word):
+    return ((word & 0x02) << 6) | ((word & 0x08) << 3) | ((word & 0x40) >> 1) | \
+        ((word & 0x80) >> 3) | ((word & 0x20) >> 2) | ((word & 0x10) >> 2) | \
+        ((word & 0x01) << 1) | ((word & 0x04) >> 2)
+
+
+def descramble_data16(word):
+    return ((word & 0x0002) << 6) | ((word & 0x0008) << 3) | ((word & 0x0040) >> 1) | \
+        ((word & 0x0080) >> 3) | ((word & 0x0020) >> 2) | ((word & 0x0010) >> 2) | \
+        ((word & 0x0001) << 1) | ((word & 0x0004) >> 2) | ((word & 0x0200) << 6) | \
+        ((word & 0x0800) << 3) | ((word & 0x4000) >> 1) | ((word & 0x8000) >> 3) | \
+        ((word & 0x2000) >> 2) | ((word & 0x1000) >> 2) | ((word & 0x0100) << 1) | \
+        ((word & 0x0400) >> 2)
+
+
+def descramble_addr(addr, width):
+    if width == 8:
+        return ((addr & 0x01) << 1) | ((addr & 0x02) << 3) | ((addr & 0x04) >> 2) | \
+            ((addr & 0x08) >> 1) | ((addr & 0x10) >> 1) | ((addr & 0x20) << 10) | \
+            ((addr & 0x40) << 4) | ((addr & 0x80) << 10) | ((addr & 0x100) << 6) | \
+            ((addr & 0x200) >> 4) | ((addr & 0x400) >> 3) | ((addr & 0x800) << 1) | \
+            ((addr & 0x1000) << 4) | ((addr & 0x2000) >> 7) | ((addr & 0x4000) << 4) | \
+            ((addr & 0x8000) >> 4) | ((addr & 0x10000) >> 3) | ((addr & 0x20000) >> 8) | \
+            ((addr & 0x40000) >> 10) | (addr & 0xFFF80000)
+    else:
+        return ((addr & 0x02) << 3) | ((addr & 0x10) >> 3) | ((addr & 0x20) << 3) | \
+            ((addr & 0x40) << 6) | ((addr & 0x80) >> 1) | ((addr & 0x100) << 5) | \
+            ((addr & 0x200) << 2) | ((addr & 0x400) >> 1) | ((addr & 0x800) << 5) | \
+            ((addr & 0x1000) >> 5) | ((addr & 0x2000) >> 8) | ((addr & 0x8000) << 2) | \
+            ((addr & 0x10000) >> 6) | ((addr & 0x20000) >> 2) | (addr & 0xFFFC400D)
+
+
+def determine_rom_type(buf):
+    if buf.startswith(b'JP-800'):
+        return 8, "JP-800"
+    elif buf.startswith(b'Roland'):
+        if buf[0xC:0xF] == b'O\xB0S':
+            return 8, "SR-JV80"
+        elif buf[0xC:0xF] == b'O\xB0X':
+            return 16, "SRX"
+        else:
+            raise ValueError(f"Unknown ROM type: {buf[0xC:0xF]}")
+    else:
+        raise ValueError(f"Invalid ROM: {buf[:6]}")
+
+
+AA = [2, 0,  3,  4,  1, 9, 13, 10, 18, 17,
+      6, 15, 11, 16, 8, 5, 12, 7,  14, 19]
+
+DD = [2, 0, 4, 5, 7, 6, 3, 1]
+
+
+
+def descramble(filename):
+    try:
+        with open(filename, 'rb') as f:
+            buf = f.read()
+    except:
+        print(f"Error: Cannot open {filename}")
+        return
+
+    #outbuf = bytearray(len(buf))
+
+    #width, rom_type = determine_rom_type(buf)
+
+    #print(rom_type + " ROM detected.")
+
+    length = len(buf)
+    dst = bytearray(length)
+    for i in range(length):
+        # clear lower 20 bits
+        address = i & ~0xFFFFF
+        # reordenar los bits del offset
+        for j in range(20):
+            if (i >> j) & 1:
+                address |= 1 << AA[j]
+        # extraer el byte de buf en la dirección calculada
+        srcdata = buf[address]
+        data = 0
+        # reordenar los bits del byte
+        for j in range(8):
+            if (srcdata >> DD[j]) & 1:
+                data |= 1 << j
+        dst[i] = data
+    return dst
+