Mapper Slots (Numbered 0:255) Event 1 to 16 (4 bits)     Source 0 1 14 15     30 31 16 17     4 bits Msg 0 Msg 1 Msg 14 Msg 15     224 225 238 239 Msg 16 Msg 17     Msg 31 Msg 32 Source 15 240 241 254 255 Sources 14, 15 may be reserved for communication Each mapper slot (0:255) points to a distinct Memory Buffer Block One event’s slots are filled or being filled; others point to empty memory After an event is finished, the mapper is set to point to new memory slots for that event (in preparation for the next time that event number is used) JTL, MSU 8/8/97