Commodore Amiga - Blitter Block Diagram

Blitter Block Diagram
Figure 6-15 shows the basic building blocks for a single bit of a 16-bit-wide operation of
the blitter.
It does not cover the line-drawing hardware.
1. The upper left corner shows how the first- and last-word masks are applied to
the incoming A-source data. When the blit shrinks to one word wide, both the
first- and last-word masks apply
to the incoming data word.
2. The shifter (upper right and center left) drawing illustrates how 16 bits of data
is taken from a specified position within a 32-bit register, based on the A-shift or
B-shift values shown in BPLCONO and BPLCONl.
3.
The minterm generator (center right) illustrates how the minterm select bits
either allow or inhibit the use of a specific minterm.
4.
The drawing shows how the fill operation works on the data generated by the
min term combinations. Fill operations can be performed simultaneously with
other complex logic operations.
5. At the bottom, the drawing shows that data generated for the destination can
be prevented from being written to a destination by using one of the blitter con-
trol bits.
6. Not shown on this diagram is the logic for zero detection, which looks at every
bit generated for the destination. If there are any I-bits generated, this logic
indicates
that the area of the blit contained at least one I-bit (zero detect is
false ).
Blitter Hardware 195