Blitter modulo for destination D
This register contains the Modulo for Blitter source (x=A,B,C) or Dest (x=D). A modulo is a number that is automatically added to the address at the end of each line, in order that the address then points to the start of the next line. Each source or destination has it's own Modulo, allowing each to be different in size, while an identical area of each is used in the Blitter operation.