Figure 6-13 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. Figure 6-13: Blitter Block Diagram * 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 masks are applied. * 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 BLTCON0 and BLTCON1 . * The minterm generator (center right) illustrates how the minterm select bits either allow or inhibit the use of a specific minterm . * The drawing shows how the fill operation works on the data generated by the minterm combinations. Fill operations can be performed simultaneously with other complex logic operations. * 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 control bits. * Not shown on this diagram is the logic for zero detection, which looks at every bit generated for the destination. If there are any 1-bits generated, this logic indicates that the area of the blit contained at least one 1-bit (zero detect is false.)
[Back to Amiga Developer Docs]