ADVANCED TOPICS
THE SKIP INSTRUCTION
The SKIP instruction causes the Copper to skip the next instruction if the video beam
counters are equal to or greater than the value given in the instruction.
The contents of the SKIP instructions words are shown below. They are identical to the
WAIT instruction, except that bit 0 of the second instruction word is a 1 to identify this as
a SKIP instruction.
FIRST INSTRUCTION WORD (IR1)
Bit 0 Always set to 1.
Bits 15 - 8 Vertical position (called VP).
Bits 7 - 1 Horizontal position (called HP).
Skip if the beam counter is equal to or
greater than these combined bits
(bits 15 through 1).
SECOND INSTRUCTION WORD (IR2)
Bit 0 Always set to 1.
Bit 15 The blitter-finished-disable bit.
(See "Using the Copper with the
Blitter" below.)
Bits 14 - 8 Vertical position compare enable bits (called VE).
Bits 7 - 1 Horizontal position compare enable bits (called HE).
The notes about horizontal and vertical beam position found in the discussion of the WAIT
instruction apply also to the SKIP instruction.
- Coprocessor Hardware 27 -
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