Description & Features
The ZVG is an Analog Vector Generator and
therefore there are no stair stepping effects.
All vectors are drawn as a smooth continuous
lines between endpoints. The vector generation
logic allows direct addressing of vector endpoints,
and unlike the Atari's AVG, there
is no vector drift.
Connecting the ZVG to an ECP
capable parallel port allows the PC to directly
drive both B&W and Color X/Y monitors,
including the B&W monitor used by the portable
Vectrex gaming platform. The ZVG hardware is
capable of 1200x1200 endpoint resolution, but
is driver limited to 1200x944 to prevent monitor
By using an analog vector
generator that allows direct endpoint addressing,
the ZVG uses the best of both worlds when comparing
a Digital Vector Generator and an Analog Vector
Generator. It uses an Analog Vector Generator
for smooth continuous vectors, and yet still
allows direct addressing of the endpoints,
like that of a Digital Vector Generator. This
allows the ZVG to emu
late all known Vector Generators, which include
the Digital Vector Generators such as Atari's
earlier B&W games, the
Sega games, and the Analog Vector Generator
used by Cinematronics (that also allowed direct
positioning of the vector starting point).
It can also emulate relative addressed vector
generators, like the analog vector generators
used by Atari.
The ZVG allows 1200x1200 addressable
endpoints. This is the hardware resolution,
and is driver limited to 1200x944, to prevent
To take into account the
4:3 viewing ratio of a standard monitor, and
to give games the ability to overscan the monitor's
edges, the ZVG is setup to use a viewable area
of 1024x768 endpoints, with the ability to
overscan the borders to 1200x944 endpoints.
Vectors that are drawn beyond the 1024x768
window will extend beyond the edges of the
monitor. A 1200x944 overscan boundary allows
vectors to be drawn 1.23" off the edge
of a 19" monitor. Overscanning was mostly
used by Atari in games like Tempest. Tempest
placed no limits on the amount of overscanning,
whereas by limiting overscanning to 1.23",
the ZVG achieves the same visual effects without
generating the possibly monitor damaging voltages
that Tempest is known for.
Full Range of X / Y Drive Voltages
The ZVG X and Y full range capabilities
are +12 / -12 volts. Through jumpers and adjustment
pots the X and Y drive voltages can be set
to drive any Arcade X / Y monitor. Also included
are adjustments for centering X and Y offsets.
65536 Colors or 64 Levels of Grayscale
The ZVG uses a 16 bit color depth.
Five bits are used for Red and Blue, six bits
are allocated for Green for a total of 65536
colors. When driving a B&W monitor, the
Green output is used as the Z-signal for a
total of 64 levels of grayscale. These values
far exceed the specifications of the monitors
being driven, allowing for full use of the
Selectable Drawing Speeds
Drawing speeds are jumper selectable
and based on the speed of vector movement on
a 19" monitor. Vector draw speed is constant,
so vector movement will be faster on larger
monitors, and slower on smaller, but the time
it takes to draw the vector will remain constant.
There are four selectable speeds: 15us / 30us
/ 40us / 50us per inch.
in Pincushion and Edge Bloom correction
properly drive the WG 6100 series monitors,
both Pincushion and Edge Bloom correction must
be used. The ZVG has jumpers to enable / disable
Software adjustable endpoint intensities allow
compensating for different yoke speeds and
allow adjusting the "look" of a vector
to taste. Some prefer bright points at the
ends of vectors, some prefer constant intensity
The ZVG firmware allows adjusting of the intensity
of a point relative to the intensity of a vector.
Once vector endpoints have been set to taste,
the point intensities can be adjusted to match.
Vector Jump Speeds
For increased efficiency, the speed at which
the CRT trace "jumps" between the
endpoint of one vector and the start of the
next can be set higher than the speed at which
a vector can be drawn. Any non-linearities
in trace movement, caused by the higher jump
speed, will not be seen since the trace is
blanked. The "between vector jump speed" is
Adjustable Color and
Grayscale Voltage Settings
The minimum and maximum allowable DAC voltages
values are under software control. This allows
setting the proper voltages needed for full
contrast and brightness for any vector monitor.
Most Arcade Game Vector monitors required similar
Z-axis voltages, however monitors such as the
Vectrex vector monitor, require non-standard
Z-axis voltages, which can be accommodated.
All Firmware Settings
Backed up in EEPROM
All setup parameters that are not
jumper selectable are save in EEPROM. This
includes such things as control of the timings
used to draw a vector, and the DAC voltages
used to generate colors and gray scales. The
settings of the these values are done using
the software utility ZvgTweak. Once setup,
the values may be stored in EEPROM. Separate
values are kept for each of the four different
monitor speeds supported by the ZVG.
Monitor Safety was
a Design Priority!
Arcade style X/Y Monitors have not
been manufactured for at least 20 years, they
are not easy to come by, and are not cheap.
Every effort has been made to protect the X/Y
monitor under normal use, and under adverse
conditions. Here's a list of monitor safety
features implemented in the ZVG:
- Safe Power On. Immediately
upon power on, or reset, all outputs are
set to a "monitor safe mode" and
remain there until all power on self tests
are completed without error. The monitor
safe mode is indicated by 0.0V on X, Y
and Z outputs (no Z-drive, the CRT trace
held at center position).
- Power On Self Tests
(POST). All EPROMs are checksummed
tested, communications between the two
onboard processors are verified, EEPROM
state values are checksummed, and ranged
tested before being accepted as valid.
- Brown out detection. Any
unsafe voltage fluctuations on the power
supply will cause the ZVG to go into the
monitor safe mode.
- Watchdog timers
on both processors. If, for
whatever reasons, either of the ZVG processors
lock up, a watchdog timer will kick in
and reset the ZVG into the monitor safe
- Vector Activity
Timeout. If no vector activity
is present on the parallel port for more
than 250ms, the ZVG will immediately
enter the monitor safe mode. This can
occur if the parallel port connector
is removed or jarred lose, or the PC
locks up or is turned off, or the PC
software crashes, etc. This prevents
the CRT trace from being held in a non-centered
position for any length of time, which
can cause a vector monitor to overheat.
It also helps guard against burn in,
in the case of a defective spotkiller,
since the monitor safe mode also turns
off the Z-drive.
Should the need arise, the ZVG's firmware is
fully user upgradeable.
X / Y Drive Voltages
Amplifone, WG Color:
RGB Z-Drive Voltages
Colors and Intensities
19" CRT Reference:
Edge Bloom Correction
Driver limited to 1200x944 endpoints
Adjustable from 0v to +/- 12v
X axis: +/- 4V, Y axis: +/- 3V
X axis: +/- 8V, Y axis +/- 6V
X axis: +/- 10V, Y axis: +/- 7.5V
1V standard, software adjustable
4V standard, software adjustable
64 levels of grayscale
15us / 30us / 40us / 50us per inch
Jumper selectable, w/Trapezoid adj
90 - 120VAC, 60Hz, 5W
18VAC @ 500ma, U.L. Listed
6" x 4-3/4" x 5/8"
parts & labor