a link-local IPv6 address uses the prefix fe80. This is described in RFC 4291. Also for other address types there is a good information RFC which provides an overview of special use addresses. It is RFC 5156.
If the MAC-based interface ID is used, it is built according to the EUI-64 format, by extending the MAC address to 64 bits by adding FF FE between the 3rd and 4th Byte and “locally administered bit” must be set (2nd bit)