BLTxMOD 064 W A Blitter modulo x
This register contains the modulo for blitter
source (xA,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).
BLTxPTH 050 W A Blitter pointer to x (high 3 bits)
BLTxPTL 052 W A Blitter pointer to x (low 15 bits)
This pair of registers contains the 18-bit address
of blitter source (x=A,B,C) or destination (x=D)
DMA data. This pointer must be preloaded with the
starting address of the data to be processed by
the blitter. After the blitter is finished, it
will contain the last data address (plus increment
and modulo).
LINE DRAW BLTAPTL is used as an accumulator
LINE DRAW register and must be preloaded with
LINE DRAW the starting value of (2Y-X) where
LINE DRAW Y/X is the line slope. BLTCPT and
LINE DRAW BLTDPT (both H and L) must be
LINE DRAW preloaded with the starting address
LINE DRAW of the line.
BPLlMOD 108 W A Bit plane modulo (odd planes)
BPL2MOD 10A W A Bit Plane modulo (even planes)
These registers contain the modules for the odd
and even bit planes. A modulo is a number that is
automatically added to the address at the end of
each line, so that the address then points to the
start of the next line.
Since they have separate modules, the odd and even
bit planes may have sizes that are different from
each other, as well as different from the display
window size.
- 264 Appendix A -
To Next Page
Loading...
