514,515 
 


     Here's a short example of a DLI. It will print the lower half of your
     text screen upside down:

     10   START = PEEK(560) + PEEK(561) *
        256: POKE START + 16,130
     20   PAGE = 1536: FOR PGM = PAGE TO P
        AGE + 7: READ BYTE: POKE PGM, BYTE
        : NEXT PGM
     30   DATA 72,169,4,141,1,212,104,64
     40   POKE 512,0: POKE 513,6: POKE 542
        86,192
     50   FOR TEST = 1 TO 240: PRINT"SEE "
        ;: NEXT TEST
     60   GOTO 60

     Another example of a DLI changes the color of the bottom half of
     the screen. To use it, simply change the PAGE + 7 to PAGE + 10
     in the program above and replace line 30 with:

     30   DATA 72,169,222,141,10,212,141,2
        4,208,104,64

     Finally, delete lines 50 and 60. See also location 54282 ($D40A).

514,515        202,203        VPRCED
     Serial (peripheral) proceed line vector, initialized to 59314
     ($E7B2), which is merely a PLA, RTI instruction sequence. It is
     used when an IRQ interrupt occurs due to the serial I/O bus
     proceed line which is available for peripheral use. According to
     De Re Atari, this interrupt is not used and points to a PLA, RTI
     instruction sequence. This interrupt is handled by the PIA chip
     and can be used to provide more control over external devices.
     See the OS Listing, page 33.

516,517        204,205        VINTER
     Serial (peripheral) interrupt vector, initialized to 59314 ($E7B2).
     Used for the IRQ interrupt due to a serial bus I/O interrupt.
     According to De Re Atari, this interrupt is not used and points to
     a PLA, RTI sequence. This interrupt is processed by PIA. See the
     OS Listing, page 33.

518,519        206,207        VBREAK
     Software break instruction vector for the 6502 BRK ($00)
     command (not the BREAK key, which is at location 17; $11),
     initialized to 59314 ($E7B2). This vector is normally used for
     setting break points in an assembly language debug operation.
     IRQ.

520,521        208,209        VKEYBD
     POKEY keyboard interrupt vector, used for an interrupt
     generated when any keyboard key is pressed other than BREAK