TS2068 Screen Addressing

To print a digit on the 2068 you must PEEK 23684 + 256 * PEEK 23685. This gives the starting addresss of the display file and must be increased by increments of 256 up until a value of 2048. To print more than one digit you can increase the original address after storing it in a register, thus it can be referenced later to allow the print position to be altered.

TO PRINT A DIGIT ON THE 2068

 10 LET n=PEEK 23684 + 256 * PEEK 23685
 20 POKE n,255
 30 LET n = n + 256
 35 IF n>= 18432 THEN STOP
 40 GO TO 20

PEEK 23688 gives the X value of the print position.

PEEK 23689 gives the Y value of the pront position.

Note that the print position 0,0 will have the value of 33,24. Position 20,0 w111 have the value of 33,3.

The screen address coordinates start at 0,0 in the lower right hand, and end at 33,24 in the upper left.

Both the ZX81 and the 2068 have the same display file layout.

  10 LET n= PEEK 23684 + 256 * PEEK 23685
  12 LET k = n
  14 LET c = 0
  20 FOR m = 1 TO 8
  30 POKE n,255
  40 LET n = n + 256
  50 NEXT m
  52 LET c = c + 1
  55 LET n = K + c
  67 IF C>=20 THEN GO TO 95
  70 GO TO 20
  95 LET c = 0
 100 LET k = * + 32
 105 LET n = k
 109 IF C>= 20 THEN STOP
 110 GO TO 20