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The actual video information for these objects is
stored in ROM K6. This ROM provides a total memory
size of 32 x 8 bits. (see Figure 3-13).
The MPU controls the positions and different
configurations of
this·
video by information that it
stores at selected addresses in the display RAM. Each
of the three motion objects corresponds to three
bytes of data stored in this RAM: one byte determines
which of the pidures in ROM is to be addressed; the
second byte determines the vertical position of that
motion object; and the third byte determines the
horizontal position of the object.
These bytes of RAM data are accessed by hori-
zontal sync signals 8H, 16H, 32H and 64H at the be-
ginning of each horizontal scan line (during the hori-
zontal blanking periqd, i.e., when 2S6H is low).
Therefore, before each horizontal line is scanned,
the motion generator receives the necessary informa-
tion to tell it what, if any, motion objects are to be
displayed on that line.
Vertical position data (DISPLAY 0-DISPLA Y 7) is
received by vertical line comparators C4 and L4.
These comparators determine if a motion object is to
be displayed on the line currently being scanned.
Take, for example, the data code for an object to be
displayed beginning on line 120. The RAM byte data
code of 01111000 would be loaded into the com-
parators. If the vertical line count (as determined by
1V, 2V, 4V, 8V, 16V, 32V, 64V and 128V) is also at
01111000, a compare signal (pin 7 of LS, low) will be
generated. This signal initiates one of the three verti-
cal load pulses at KB, LDV1A, LDV2A, and LDV3A.
These vertical load pulses are used to load the ROM's
video information into appropriate video shift
registers.
In review, for each ball, the motion object
generator receives one byte of RAM data (DISPLAY
0-7 going to C4 and L4) that controls where that
object is to be displayed vertically. The generator
receives a second byte of RAM data (DISPLAY 7 going
to ROM K6) that selects the ball picture to be dis-
played. The correct video information for that picture
(VID S-7) is then loaded into the appropriate shift
register (N7 for ball 1, L7 for ball 2, and J7 for ball 3).
A third byte of RAM data is necessary to deter-
mine where the object picture is to be placed hori-
zontally. This data (DISPLAY 0-7) is loaded into a pair
of horizontal counters (RS and R6 for ball 1, PS and P6
for ball 2, and NS and N6 for ball 3). These counter
pairs are preset when the horizontal scan of that line
begins (2S6H* goes high). The counters begin count-
ing up at the rate of 6 MHz. When the counter pair
reaches a specific point in its count sequence, it gen-
r - -
MOT10N'OBJECT'GENE'RATo_R_
I
I
I
I
I
DISPLAY 0-7
FROM
DISPLAY
0-7
DISPLAY - - - - - -
RAM
0-7
DISPLAY
7
I
HORIZONTAL
LOCATION
COUNTERS
VERTICAL
LOCATION
COUNTERS
SHIFT OUT
PICTURE DATA
LOAD
PrCTURE
DATA
PICTURE DATA
MOTIOt~
OBJECT _____ v_1D_s_-v_1D_1 _ _ _ _
PICTURE
ROM
L _ _
Figure 3-13 Motion Generator Circuit, Simplified Diagram
MOTION OBJECTS
I
VID_
EO
(BALL
1,
2, & 3)
I
I
I
_J
Super Breakout 3 -13
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