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The WAIT Instruction
The WAIT instruction causes the Copper to wait until the video beam counters are
equal to (or greater than) the coordinates specified in the instruction. While waiting, the
Copper is off the bus and not using memory cycles.
The first instruction word contains the vertical and horizontal coordinates of the beam
position. The second word contains enable bits that are used to form a "mask" that
tells the system which bits of the beam position to use in making the comparison.
FIRST INSTRUCTION WORD (IRl)
Bit 0
Always set to 1.
Bits 15 - 8
Vertical beam position (called VP).
Bits 7 - 1
Horizontal beam position (called HP).
SECOND INSTRUCTION WORD (IR2)
Bit 0
Always set to O.
Bit 15
The blitter-finished-disable bit.
Normally, this bit is a 1.
(See the "Advanced Topics" section below.)
Bits 14 - 8
Vertical position compare enable bits (called VE).
Bits 7 - 1
Horizontal position compare enable bits (called HE).
The following example WAIT instruction waits for scan line 150 ($96) with the horizon-
tal position masked off.
DC.W
$9601,$FFOO
i
Wait for line 150,
i
ignore horizontal counters
The following example WAIT instruction waits for scan line 255 and horizontal position
254. This event will never occur, so the Copper stops until the next vertical blanking
interval begins.
DC.W
$FFFF ,$FFFE
i
Wait for line 255,
i
H
= 254
(ends Copper list)
Coprocessor Hardware 11
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