BLTDDAT Blitter destination data register
This register holds the data resulting from each
word of blitter operation until it is sent to a
RAM destination. This is a dummy address and
cannot be read by the micro. The transfer is
automatic during blitter operation.
BLTSIZE 058 W A Blitter start and size (window width, height)
This register contains the width and height of
the blitter operation (in line mode, width must
= 2, height = line length). Writing to this
register will start the blitter, and should be
done last, after all pointers and control
registers have been initialized.
BIT 15,19,13,12,11,10,09,08,07,06,05,04,03,02,01,00
---------------------------------------------------
h9 h8 h7 h6 h5 h4 h3 h2 h1 h0,w5 w4 w3 w2 w1 w0
h=height=vertical lines (10 bits=1024 lines max)
w=width=horizontal pixels (6 bits=64 words=1024 pixels max)
LINE DRAW BLTSIZE controls the line length and starts
LINE DRAW the line draw when written to. The h field
LINE DRAW controls the line length (10 bits gives
LINE DRAW lines up to 1024 dots long). The w field
LINE DRAW must be set to 02 for all line drawing.
BLTxDAT 074 W A Blitter source x data register
This register holds source x (x=A,B,C) data for
use by the blitter. It is normally loaded by the
blitter DMA channel; however, it may also be
preloaded by the microprocessor.
LINE DRAW BLTADAT is used as an index register
LINE DRAW and must be preloaded with 8000.
LINE DRAW BLTBDAT is used for texture; it must
LINE DRAW be preloaded with FF if no texture
LINE DRAW (solid line) is desired.
- Appendix A 263 -
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