UGV - AtariBits

UGV-II Ultimate Gated Video Board

Back in the days of CRT TV's the visible image was cropped by what was called 'over scan' wrapped around the edges of the CRT picture tube. Later when computer monitors got cheaper, more people starting using them instead of their TV's. The side effect of this transition resulted in less of the over scan image being chopped off. To this day the trend has continued with the advent of modern HDTV's, which now display every bit of possible video coming out of the Atari 8-bit.

As a result, some games and applications that take advantage of this normally 'hidden' area of the screen to hide various graphics manipulations (akin to racing the beam), now have all these unsightly artifacts revealed. So the main idea behind the UGV-II board is to hide these areas that were never meant to be seen, by 'blanking' them out. As part of its operation it also incorporates an entirely new HQ Video Driver Circuit with both composite and S-Video output quality being similar to what is seen in the UAV board created by AtariAge member Bryan.

The UGV-II board is meant to piggyback the existing GTIA chip Atari P/N: CO14805 [NTSC] or CO14889 [PAL], thus providing a 'no solder' installation in the XL series machines. XE systems will require de-soldering the GTIA chip and installing a 40 pin socket, or in the case of the 400/800 the UGV board will get soldered directly in place of the GTIA chip due to limited space.

Go to: Original Older UGV Information

O-Scope showing Video Gate signal vs. Video Output

Follow the Discussion on AtariAge
...Still working on GTIA V-Gate?

Microchip PIC V-Gate Timing Generator...

Precise timing of the video gating aspect is performed by an embedded PIC MCU clocked by the GTIA's OSC pin, and then boosted by a factor of 4x by an internal PLL. This synced high speed clock makes it possible to execute code in the PIC chip quickly enough to allow gating of the video signal at just the right moment in order to eliminate over scan by switching off the Luma and Chroma before subsequently being buffered and sent to the video outputs. This gating can be disabled by grounding pin-7 on J1 (VGATE OFF). And if left open, a +5V pull-up resistor creates an enabled state, or in other words turns VGATE ON (default). An unused RF channel switch can be used for toggling this function.

The PIC VGATE chip requires firmware flashing out of circuit. And afterwards is plugged into the 8-pin DIP socket on the UGV-II video board for automatic VGATE operation.

VGATE CHIP

Simple But Effective HQ Video...

FMS6400 Block Diagram

The basis of the video driver circuit is the FMS6400 a Dual Channel Y/C Video Driver and Composite Video Summer IC chip. Basically you just feed it the proper level of the Luma 'Y' following a resistor DAC in our case, and the Chroma 'C' to get fully DC restored and filtered 75 ohm impedance video out the other end. At the same time a 3rd buffered output sums the 'Yin' and the 'Cin' to create an independent composite 75 ohm impedance video output. Since the input side of the FMS6400 is at a relatively high impedance, it eliminates the need for additional emitter follower transistor circuits and greatly simplifies the overall design of the video circuit as compared to what Atari did.

To insure that the minimum amount of noise gets introduced in this process, the FMS6400 is used in its 0 db gain mode, while the resistor DAC is composed of very low ohm values driven by a SN74F08N Quad 'AND' Gate having much higher drive current than the CD4050 buffer chip used in the original Atari video circuit.

Using the low ohm (low impedance) resistors for the DAC's ladder makes them far less susceptible to picking up switching noise from the immediate area. The overall result produces very clean noise-free video while keeping the signal paths simple and direct.

Although the FMS6400 is an obsolete chip, it really does such a superb job for this application that it's worth buying NOS from the likes of eBay or AliExpress. And it's readily available from those sources, being sold at a very reasonable cost of less than $1.00 each (that price includes shipping when purchased in lots of 5 pieces or more). It's commonly sold as FMS6400, FMS6400CS, FMS6400CS1 which are all essentially the same part.

Female to Female Jumper Wires

Installation: 600XL, 800XL, and 1200XL is Extremely Easy and Virtually Solder-less..
When a fully assembled board is piggybacked with the Atari's GTIA chip, the UGV-II instantly becomes a fully functional device with minimal external connections required other than the video outputs. Which in most cases consists of a couple of soldered points on the Atari motherboard in order to feed the stock 5-pin DIN A/V jack (reference TBA's UAV manual for locations).

And for those that wish to have an industry standard S-Video Mini-DIN connection, there's also an optional solder-less interface board available that enables a simple plug-in interconnection utilizing pre-made off the shelf jumper wires (check out the BOM for a source of these).

Installation in XE Series Systems without sockets, Requires Soldering & De-soldering Skills...
The XE line of computers never had the IC chips socketed (might also apply to certain 600/800XL systems), and thus will require desoldering of the GTIA chip and installation of a 40 pin IC socket in its place. This IC socket should preferably be a machine pin type as shown in the image below.
GTIA 40-pin IC Socket Suggested Vendors and Part Numbers...

Jameco Part no.: 41136
Digi-Key Part no.: ED3032-ND
Mouser Part No.: 575-1104764041001000

400/800 Special Considerations: Even though the UGV-II utilizes a low profile piggyback design, the 400/800 computers have such severe space constraints due to the cast aluminum RF shielding surrounding the plug-in cards, that the GTIA's socket needs to be removed (de-soldered). After doing so, the UGV-II board needs to get soldered directly in its place, and then plug the GTIA chip into the UGV-II's socket instead. Depending upon which CPU board is in use, header J1 might need to be eliminated and the wires soldered directly to the board. Obviously a lot of compromises are required for these older systems, making them better suited for a UAV instead.

This is Meant to Replace Your Stock Atari Video...
The UGV-II's video output is far superior to the stock video coming out of your Atari, and is really meant to be a complete replacement for it. However the UGV-II can co-exist.

Since the UGV-II is all about getting High Quality video output, there's no longer a need for the original stock video outputs. In fact it just makes good sense to cut loose the original video connections going to the A/V jack, and instead route the UGV-II video outputs to that same jack.

The Brewing Academy has an installation pdf manual for their UAV product that does a good job of showing how to eliminate the connection of the A/V jack to the stock video, and then take it over for the UAV. This same method will also work for the UGV-II.

The UGV-II is designed to be used with a "real" GTIA chip, and therefore might not be compatible with Sophia 2's virtual GTIA. Although it works just fine with previous Sophia versions, including the dedicated Sophia-DVI.

The Brewing Academy

A great source of after market Atari products

The Brewing Academy will probably sell completely assembled and fully tested versions of the UGV-II or provide a DIY bare board kit with the FMS6400 SMD already pre-soldered to the board. This is a newer version, so give them time to stock it - or request that they carry it.

Alternate Version
There is also a smaller footprint fully SMD counterpart designed by AtariAge member: Overange, available from PCBway
(will be coming soon).