DESKTOP x1k12
                                ͻ
                                     SHIFTER     
                                 bit assignments 
                                ͼ
                                 Atari SHIFTER
              Ŀ
               SYNChronization      b9=frequency (synchronization=internal)
                                       -:             (resolution=high)
                                                        frequency=71 Hz
                                                           screen=501 lines
                                                             line=28 s
                                                   display enable=line 36 &
                                                                  col. 0 s
                                       0:             (resolution=medium/low)
                                                        frequency=60 Hz
                                                           screen=263 lines
                                                             line=63.5 s
                                                   display enable=line 35 &
                                                                  col. 6.5 s
                                       1:             (resolution=medium/low)
                                                        frequency=50 Hz
                                                           screen=313 lines
                                                             line=64 s
                                                   display enable=line 48/64 &
                                                                 =col. 7 s
                                    b8=synchronization
                                       0:internal
                                       1:external
              
                   Ŀ
                    RESolution   b9-b8=resolution
                                       00:low
                                       01:medium
                                       10:high
                   
                   Ŀ
                    Video Base [b23-b8]=video base
                   
                Ŀ
                 Video Counter [b23-b0]=video counter
                                        (1 word read each 500 ns)
                                        (when display enable)
                                        (without wait state for MC68000)
                
               Ŀ
                Color Register  b10-b8=[b2-b0]=red   level
                                 b6-b4=[b2-b0]=green level
                                 b2-b0=[b2-b0]=blue  level
                                             (resolution=high   CR0b0=Ink    )
                                             (                        0:white)
                                             (                        1:black)
                                             (resolution=medium CR0-CR3  used)
                                             (resolution=low    CR0-CR15 used)
               
