http://vinace.sourceforge.net/en-x1290.html#AEN1744 9.3.8.2 Addresses repeats 0x81 > In any case, it's easily tested with a short sequence that reads a > location, inverts it, stores it, then reads it again and compares. If it's > changed, re-invert it and note that writes are enabled. Unless the ROM is active, then you can't initially read the RAM to determine the original value.