TM 1-1510-225-10 3B-37 Table 3B-8.  FMS-800 CDU Function and Application Keys FUNCTION KEYS KEY DESCRIPTION KEY DESCRIPTION COM Accesses    control    pages    for    UHF/VHF radio. M3 Function not used. DATA Enables display of expanded data for any selected waypoint. MARK Marks   and   stores   present   position   plus any    active    cursor    position    transmitted from the Flight Display System (FDS). DIR Enables  immediate  selection  of  Direct-To waypoint. MSN Accesses  a  menu  of  additional  mission functions. EDIT Accesses Flight Plan pages. NAV Accesses the Navigation information page. FPLN Accesses Flight Plan pages. PSN Accesses  Pilot  Position  (present  position and track) pages. IDX Accesses index of additional functions not available on top-level keys. STAT Accesses avionics LRU status pages. IFF Function not used. STR Accesses Pilot Steering pages. INAV Accesses  comprehensive  data  pages  for GPS navigation solutions. APPLICATION KEYS – Deletes  data  from  entry  fields  or  causes data to revert to a default value. ¯ Scrolls  vertically  to  related  pages  of  data or  scrolls  down  through  lists  of  data  on  a page. CLR Clears  the  scratchpad  of  incorrect  entries or annunciations. ® Horizontally scrolls right to access additional pages of information. / Separates the waypoint identifier, bearing, and distance components. ¬ Horizontally scrolls left to access additional pages of information. - Scrolls  vertically  to  related  pages  of  data or  scrolls  up  through  lists  of  data  on  a page. (a)  Scratchpad.      The   scratchpad   is   a buffer to hold all data for review prior to executing the input.  As data is keyed into the CDU with the keypad, the entered values are displayed within the scratchpad field at the bottom of the display.  Incorrect entries are cleared with the   CLR  key.    A  single  press  clears  the last character on the right.  Holding the  CLR key down clears   the   entire   scratchpad.      The   scratchpad   is cleared  automatically  when  the  system  accepts  valid inputs. (b)  Function Keys.  The labeled function keys are used to call up specific top-level pages of the CDU  and  to  simultaneously  dedicate  the  line  select keys     to     the     functions     indicated     on     that     page.   Exceptions are the   MARK,  DATA, and   M3  keys  that do not change the page but do initiate their respective functions.    Some  functions  which  are  less  frequently used  in  flight  are  accessed  through  the  index  (IDX) and  flight  plan  edit  (EDIT)  function  keys  and  then  via line  select  keys  on  the  respective  menu  page.    The Index and Flight Plan Edit pages are shown in Figure 3B-18. (c)  Line  Select  Keys.    Line  select  keys can   be   used   to   access   lower   level   pages,   toggle modes  of  the  function,  enter  data  in  the  associated field, or copy data in the scratchpad.  When undefined line select keys are pressed, no operation is performed and no annunciation is displayed.