562



     The above bits may be combined (i.e., DLI, scrolling and LMS
     together) if the user wishes.

     Special DL instructions (with decimal values):
     Blank 1 line  =  0   5 lines =  64
           2 lines = 16   6 lines =  80
           3 lines = 32   7 lines =  96
           4 lines = 48   8 lines = 112

     Jump instruction (JMP) = zero (three-byte instruction).
     Jump and wait for Vertical Blank (JVP) = 65 (three-byte
     instruction).
     Special instructions may be combined only with DL interrupt
     instructions.

     A Display List Interrupt is a special form of interrupt that takes
     place during the screen display when the ANTIC encounters a
     DL instruction with the interrupt BIT 7 set. See location 512
     ($200) for DLI information.

     Since DL's are too large a topic to cover properly in this manual,
     I suggest you look in the many magazines (i.e., Creative
     Computing, July 1981, August 1981; Micro, December 1981;
     Softside, #30 to 32, and BYTE, December 1981) for a more
     detailed explanation

562            232            SSKCTL
     Serial port control register, shadow for 53775 ($D20F). Setting
     the bits in this register to one has the following effect:

     Bit    Decimal    Function
     0          1      Enable the keyboard debounce circuit.
     1          2      Enable the keyboard scanning circuit.
     2          4      The pot counter completes a read within two
                       scan lines instead of one frame time.
     3          8      Serial output transmitted as two-tone instead
                       of logic true/false (POKEY two-tone mode).
     4-6    16-64      Serial port mode control.
     7        128      Force break; serial output to zero.

     Initialized to 19 ($13) which sets bits zero, one and four.

563            233            SPARE
     No OS use. See the note at location 651 regarding spare bytes.

564            234            LPENH
     Light pen horizontal value shadow for 54284 ($D40C). Values
     range from zero to 227.

565            235            LPENV
     Light pen vertical value: shadow for 54285 ($D40D). Value is the