One change was to escape a small set of control characters, DLE, XON, XOFF and SYN. These were escaped by inserting a DLE in front of them, and then modifying the character by XORing it with 64. In theory, this meant the packet might be as long as 264 bytes if it originally consisted entirely of characters that required escaping. These inserted and modified characters are not part of the CRC calculation, they are removed and converted at the receiving end before calculating the CRC.