This register contains the modulo for blitter
source (x=A,B,C) or destination (x=D). A modulo
is a number that is automatically added to the
address at the end of each line, to make the
address point to the start of the next line. Each
source or destination has its own modulo, allowing
each to be a different size, while an identical
area of each is used in the blitter operation.
LINE DRAW BLTAMOD and BLTBMOD are used as slope
LINE DRAW storage registers and must be preloaded
LINE DRAW with the values (4Y-4X) and (4Y)
LINE DRAW respectively. Y/X= line slope.
LINE DRAW BLTCMOD and BLTDMOD must both be
LINE DRAW preloaded with the width (in bytes)
LINE DRAW of the image into which the line is
LINE DRAW being drawn (normally two times the
LINE DRAW screen width in words).
SEE ALSO: Blitter programming