Atari STEEPLECHASE, Руководство по эксплуатации, техническому обслуживанию и ремонту

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3.4.10 HORSE VIDEO (SHEET 2 ZONES A THROUGH
D
1,2,3):
Two read-only memories (ROMs) in locations C4
and D4 have been programmed with a total of six horse
figures: one jumping, one falling and four different running
figures. The choice of which figure is to be read out from
each ROM is under control of the signals applied to the
ROM's AS, A6, and A7 address inputs.
The gallop rate signals Xl through X4 generated by the
IC device in location F7 arc proportional to the 1 /2 TRACK
CLOCK signal. To produce the GALLOP A and GALLOP B
signals, the X3 and X4 signals are added to the vertical sync
chain's 64V and 32V signals, respectively. The GALLOP A
and GALLOP B signals are then combined with a composite
JUMP signal from HS pin 15 and a composite FALL signal
from J 5 pin 15, respectively, to produce the signals that
will select the horse figure to be read out from the ROMs
(refer to Figure 3-5).
During horizontal blanking the data from the ROMs for
the current line of video are loaded into the shift registers
in locations CS and DS. When a composite TC signal is
received from P8 pin 14, the shift registers are enabled to
shift the video out. The video is gated with an enable signal
which only allows the enabled horses to be displayed, and
the composite HORSES signals appears at F3 pin 12.
3.4.11 OTHER VIDEO CIRCUITRY (SHEET 2 ZONE
A,B 1 AND 2):
The racetrack portion of the composite
video is produced at A3 pin 6 by the gating of the TRACK
signal, coming from C3 pin 15 in the vertical sync chain, and
the two signals Tl and T2 coming from the racetrack motion
counter (A2 pins 14 and 13). This is the portion of the video
that produces the dotted line effect on the TV screen.
Comp
Comp
JUMP*
FALL* GALLOP A GALLOP B
l
0
X
X
0
I X
X
0 0
0 0
0 0
()
I
0
0
I
0
0 0
I
I
The finish line portion of the composite video is pro­
duced at A3 pin 11 by gating the FINISH LINE signal, coming
from B4 pin 6 in the horizontal sync chain, with the exclu­
sive OR of signals 2H and 2V. This produces the checkered
effect on the TV screen.
The pickets arc produced by gating the PICKET LINE
signal, coming from B1 pin 15, with the vertical sync chain's
16V, 8V, and 4V signals. This produces the PICKET signal
at B3 pin 6 and also the stubby picket seen on the TV screen.
The above signals are ORed together at 83 pin 10 and
then gated with a signal coming from FS pin 15. This signal
from FS has components which come from N8 pin 14 and
causes the winning horse to blink, includes the VBLANK,
HBLANK and 16V (the space between horses) from C6 pin 8,
and enables only those horses which have received credit.
The video signal produced at 84 pin 8 is then mixed with
the composite sync signal produced at E4 pin 10. The signal
resulting at the junction of resistors R 10 and R 11 is sent to
the TV monitor as the composite video output.
3.4.12 COIN CIRCUITRY (SHEET 1 ZONE A,B 4 AND 5):
The signals coming from the coin switches arc debounced
and verified to have a length of at least 20 milliseconds by
the analog circuitry connected between the edge connector
pins
(N
and 13) and the amplifiers, J9 pin 14 ,rnd J9 pin 13.
The outputs from these amplifiers is then combined to pro­
duce the COIN signal at ]8 pin 11. This signal sets the credit
latch formed by the two amplifiers with outputs at J9 pin 1
and ]9 pin 2. Transistor Q4's circuit provides the credit
latch with static �harge sensing. By comparing the diode
02\ drop voltage at ]9 pin 5 to the resistor divider voltage
at )9 pin 4, the credit latch also has power fault (power on)
reset. At the end of the game the signal produced at
DJ
pin
3 resets the credit latch.
3 MSB of ROM Address
A7 A6 AS 1-"IGURL
I
0 0
Jumping Hor,e
1
0
I Falling Horse
0 I
0
Running Horse #3
()
0 0 Running Horse# I
0
1
I
Running Hor,c ±:4
0
0
I
Running Ho1 sc ±::2
I 1 0 ( unprogr,1mmcd)
1 I
I ( un progr.i mmcd)
'Comp JUMP ,ind Comp I ALL .trL' mu1uc1llv c:-;clu,ivc, i.
e
.
Lctnnot buth be" I."
Figure 3-5 Address Coding for
ROM
s