As a coprocessor, the Copper adds its own instruction set to the instructions already provided by the 680x0 CPU. The Copper has only three instructions, but you can do a lot with them: * WAIT for aspecific screen position specified as x and y coordinates. * MOVE animmediate data value into one of the special-purpose registers. * SKIP . the next instruction if the video beam has already reached a specified screen position. All Copper instructions consist of two 16-bit words in sequential memory locations. Each time the Copper fetches an instruction, it fetches both words. The MOVE and SKIP . instructions require two memory cycles and two instruction words each. Because only the odd memory cycles are requested by the Copper, four memory cycle times are required per instruction. The WAIT instruction requires three memory cycles and six memory cycle times; it takes one extra memory cycle to wake up. Although the Copper can directly affect only machine registers, it can also affect memory indirectly by setting up a blitter operation. More information about how to use the Copper in controlling the blitter can be found in the sections called Control Register and Using the Copper with the Blitter . The WAIT and MOVE instructions are described below. The SKIP instruction is described in the "Advanced Topics" section.
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