If the Copper is used to start up a sequence of blitter operations, it must wait for the blitter-finished interrupt before starting another blitter operation. Changing blitter registers while the blitter is operating causes unpredictable results. For just this purpose, the WAIT instruction includes an additional control bit, called BFD (for blitter finished disable). Normally, this bit is a 1 and only the beam counter comparisons control the WAIT . When the BFD bit is a 0, the logic of the Copper WAIT instruction is modified. The Copper will WAIT until the beam counter comparison is true and the blitter has finished. The blitter has finished when the blitter-finished flag is set. This bit should be unset with caution. It could possibly prevent some screen displays or prevent objects from being displayed correctly. For more information about using the blitter, see Chapter 6, Blitter Hardware .
[Back to Amiga Developer Docs]