Atari Jaguar csync TTL?
Atari Jaguar csync TTL?
So I got in a loaner Jaguar with all sorts of RGB cables: sync on composite, csync, and sync on luma. The maker of the sync on luma cable claims the csync coming out of the jaguar is TTL level. Indeed when I do some Googling online, I find this document which states the same thing:
http://old.pinouts.ru/Video/AtariJaguarAV_pinout.shtml
So it sounds like it does output TTL csync, right? Well I opened the csync RGB cable from https://www.retrogamingcables.co.uk/ and determined there's no attenuation of the csync on their PCB board in the SCART head. The trace literally goes from csync pad to the sync pin with no visible components to attenuate the signal. Could they possibly have put the components in the console side of the cable, or did they simply forgot, or does the Jaguar not output TTL sync?
Very curious about this...
http://old.pinouts.ru/Video/AtariJaguarAV_pinout.shtml
So it sounds like it does output TTL csync, right? Well I opened the csync RGB cable from https://www.retrogamingcables.co.uk/ and determined there's no attenuation of the csync on their PCB board in the SCART head. The trace literally goes from csync pad to the sync pin with no visible components to attenuate the signal. Could they possibly have put the components in the console side of the cable, or did they simply forgot, or does the Jaguar not output TTL sync?
Very curious about this...
Re: Atari Jaguar csync TTL?
Update: just checked the retro gaming cable with my multimeter and there's ZERO resistance from console-side csync pin to SCART pin in the cable. So either they missed this, or the documents about Atari csync being TTL are wrong?
Edit: Here's yet another scanned page from a technical manual:
So yeah, if you have an RGB csync cable for the Jaguar from retro gaming cables, better check that csync!
Edit: Here's yet another scanned page from a technical manual:
So yeah, if you have an RGB csync cable for the Jaguar from retro gaming cables, better check that csync!
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maxtherabbit
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Re: Atari Jaguar csync TTL?
it has hsync and csync but no vsync? that's odd
Re: Atari Jaguar csync TTL?
Csync is technically the vsync line. I will try to sit down and measure the output sometime today to verify that it's 5 volts but I'm pretty sure it is and just a misstep on retrogamingcables.co.uk's part. I wasn't impressed when I dissected one of their cables sometime back.
Re: Atari Jaguar csync TTL?
I contacted retro gaming cables, and heard back from a "Robert Fletcher". He claims it does not output TTL csync, but doesn't have his notes on hand to make sure. He said he will double check and get back to me.
Edit: I found an online Atari schematic for the Jaguar that suggests the csync pin is actually "VSL" and the only thing between it and the "Tom" processor is an FB inductor "L13". So apparently vertical sync on the Jaguar also doubles as csync? I guess there's maybe a setting in the Jaguar to set this pin to vertical or csync?
Edit: I found an online Atari schematic for the Jaguar that suggests the csync pin is actually "VSL" and the only thing between it and the "Tom" processor is an FB inductor "L13". So apparently vertical sync on the Jaguar also doubles as csync? I guess there's maybe a setting in the Jaguar to set this pin to vertical or csync?
Re: Atari Jaguar csync TTL?
First report came in from a user that measured indeed 5V TTL on pin 5B using his scope. So yeah, we need to get this sorted asap for csync RGB cable users...
Edit: Person wasn't measuring under load, so we still need someone with a scope and proper load testing to get an answer on this.
Edit: Person wasn't measuring under load, so we still need someone with a scope and proper load testing to get an answer on this.
Re: Atari Jaguar csync TTL?
Found the entire original technical reference document that was written by Atari corporation in 1995:
http://atariage.com/forums/index.php?ap ... _id=369078
Page 8 has the information I showed in the earlier image.
However, another technical manual written in 2001 independently has this to say about pin 32 of the "Tom" chip: 2mA output/TTL input.
So I don't know what to make of that.
http://atariage.com/forums/index.php?ap ... _id=369078
Page 8 has the information I showed in the earlier image.
However, another technical manual written in 2001 independently has this to say about pin 32 of the "Tom" chip: 2mA output/TTL input.
So I don't know what to make of that.
Re: Atari Jaguar csync TTL?
Got a reply from someone on the Atariage forums:
Yes, it is a logic level 2 mA output from Tom, without any buffering. So it's fine to drive a high-impedance sync input (a few kΩ or higher) directly, but not for a 75Ω input.
In the latter case, you should use a series 1200Ω resistor to drop the level to the standard 300 mVpp. But I wouldn't recommend it, since without a buffer it's not suited to drive a cable...
So that kind of shocks me (pun not intended) that it would need 1.2k Ohms instead of the typical 470 Ohms. Also he suggests there's no 'buffer', so I'm curious what would be needed to build one in the cable?
The mystery continues!
Yes, it is a logic level 2 mA output from Tom, without any buffering. So it's fine to drive a high-impedance sync input (a few kΩ or higher) directly, but not for a 75Ω input.
In the latter case, you should use a series 1200Ω resistor to drop the level to the standard 300 mVpp. But I wouldn't recommend it, since without a buffer it's not suited to drive a cable...
So that kind of shocks me (pun not intended) that it would need 1.2k Ohms instead of the typical 470 Ohms. Also he suggests there's no 'buffer', so I'm curious what would be needed to build one in the cable?
The mystery continues!
Re: Atari Jaguar csync TTL?
Where are they getting 300mv pp??
I thought the standard sat around 600mv pp??
You can make a buffer by copying this design, Ive done it for heaps of my systems now.
http://www.raphnet.net/electronique/dre ... dricas.gif
Supply's clean strong TTL and keeps every safe. Put a 470R on the end if you want around 600mv pp sync.
Available chips are much smaller and a different pinout.
Be sure to ground all unused inputs.
I thought the standard sat around 600mv pp??
You can make a buffer by copying this design, Ive done it for heaps of my systems now.
http://www.raphnet.net/electronique/dre ... dricas.gif
Supply's clean strong TTL and keeps every safe. Put a 470R on the end if you want around 600mv pp sync.
Available chips are much smaller and a different pinout.
Be sure to ground all unused inputs.
Re: Atari Jaguar csync TTL?
Composite video is 1Vpp but the sync part of the signal is 0.3Vpp so if you're sending a composite sync signal to a composite video input, that's the voltage level you want to have and assuming the source is actually 5V, a 1.2K (1175 ohm) resistor is in fact required in series with it.
Re: Atari Jaguar csync TTL?
Well you better let Tim Borti Voultar ect know this because all there boards output 600mv pp 75R Csync...
Seriously though, 470R is all I require from a buffer or from an Extron to get 600mv pp.
1.2k seems like overkill and I bet causes issues.
Seriously though, 470R is all I require from a buffer or from an Extron to get 600mv pp.
1.2k seems like overkill and I bet causes issues.
Re: Atari Jaguar csync TTL?
I’ve designed my boards to output 300mV@75load on CSync. However, everything in between of 1V and 200mV should work fine on virtually all 75ohm sync inputs.
You may want to take a look into the TSH122ICT, which is signal channel video buffer with +6dB gain. You just need a handful of components around it: two resistors (e.g. 9.53kohm and 620ohm) for signal attenuation at the input, two decoupling caps on the power rail (10uF and 0.01uF) and output components (22uF, 33uF and 75ohm resistor). The IC is relatively small and does not need that much space. Place the buffer at the console end of the console!FBX wrote:Got a reply from someone on the Atariage forums:
Yes, it is a logic level 2 mA output from Tom, without any buffering. So it's fine to drive a high-impedance sync input (a few kΩ or higher) directly, but not for a 75Ω input.
In the latter case, you should use a series 1200Ω resistor to drop the level to the standard 300 mVpp. But I wouldn't recommend it, since without a buffer it's not suited to drive a cable...
So that kind of shocks me (pun not intended) that it would need 1.2k Ohms instead of the typical 470 Ohms. Also he suggests there's no 'buffer', so I'm curious what would be needed to build one in the cable?
The mystery continues!
Re: Atari Jaguar csync TTL?
So the basic gist of this all is: Jaguar RGB csync cables that just pass VSL straight to the SCART head pin are doing it completely wrong, correct?
Re: Atari Jaguar csync TTL?
If "it is a logic level 2 mA output from Tom, without any buffering" is a correct fact, than yes: passing it directly through a cable into a TV (or other 75ohm terminated input) is copletely wrong.
Re: Atari Jaguar csync TTL?
Robert of retro gaming cables reported back with this to say:
My engineer Charlie measured 700mv peak to peak under load however the output is a high impedance which doesn’t match 75 ohm so even though the voltage is with the tolerance the impedance doesn’t match. I was unaware of this when we first designed this cable CSYNC cable.
So this could be solved with a buffer or an lm1881 attached to the sync over composite. We will redesign our CSYNC version.
-FBX
My engineer Charlie measured 700mv peak to peak under load however the output is a high impedance which doesn’t match 75 ohm so even though the voltage is with the tolerance the impedance doesn’t match. I was unaware of this when we first designed this cable CSYNC cable.
So this could be solved with a buffer or an lm1881 attached to the sync over composite. We will redesign our CSYNC version.
-FBX
Re: Atari Jaguar csync TTL?
What does this mean for those of us with the current Csync cables? Any chance of Robert coming in here and commenting?
Re: Atari Jaguar csync TTL?
It means you've permanently damaged whatever equipment you used them on. Throw out those devices and star over.Johnpv wrote:What does this mean for those of us with the current Csync cables? Any chance of Robert coming in here and commenting?
On a more serious note, the experts can correct me if I'm wrong, but I believe the impedance mis-match is less 'dangerous' than a voltage one. Not sure though.
Re: Atari Jaguar csync TTL?
FBX wrote:It means you've permanently damaged whatever equipment you used them on. Throw out those devices and star over.Johnpv wrote:What does this mean for those of us with the current Csync cables? Any chance of Robert coming in here and commenting?
On a more serious note, the experts can correct me if I'm wrong, but I believe the impedance mis-match is less 'dangerous' than a voltage one. Not sure though.
*throws all my av equipment in the trash*
I was kind of more wondering if RGC would end up replacing or fixing the cables of those of us with the old version, or if we'd have to buy new cables.
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maxtherabbit
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Re: Atari Jaguar csync TTL?
I wouldn't call an impedance mismatch dangerous, but it would mean more signal degradation over longer runsFBX wrote:It means you've permanently damaged whatever equipment you used them on. Throw out those devices and star over.Johnpv wrote:What does this mean for those of us with the current Csync cables? Any chance of Robert coming in here and commenting?
On a more serious note, the experts can correct me if I'm wrong, but I believe the impedance mis-match is less 'dangerous' than a voltage one. Not sure though.
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Re: Atari Jaguar csync TTL?
If anybody wants to return their Jaguar cable for modification please return to the following address and quote your name and email address and order number if you can locate this.
Retro Gaming Cables Limited
151-153 Wincolmlee
Hull
East Yorkshire
HU2 0HD
United Kingdom
Unfortunately we cannot rewire the Jag cables for sync over luma, as the edge connectors are over-moulded, however, we can rewire it for either sync over composite video, or if you want to maintain a CSYNC signal we can rewire as follows.
11B (Composite video) --> LM1881 --> 470Ω --> SCART pin 20.
The customer will need to pay for sending the cable back to us. However we will carry out this work for free and will not charge for sending the cable back to you.
Rob
Retro Gaming Cables Limited
151-153 Wincolmlee
Hull
East Yorkshire
HU2 0HD
United Kingdom
Unfortunately we cannot rewire the Jag cables for sync over luma, as the edge connectors are over-moulded, however, we can rewire it for either sync over composite video, or if you want to maintain a CSYNC signal we can rewire as follows.
11B (Composite video) --> LM1881 --> 470Ω --> SCART pin 20.
The customer will need to pay for sending the cable back to us. However we will carry out this work for free and will not charge for sending the cable back to you.
Rob
Re: Atari Jaguar csync TTL?
Ste from HD Retrovision was kind enough to run scope and spice tests on the Jaguar pin 5B, his results suggest all you need is a series 680 Ohm Resistor and series 220uF capacitor. No need for logic buffers as this should be plenty sufficient.
Re: Atari Jaguar csync TTL?
I'll probably end up just waiting till the new version of the cables are available and order a new one.
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maxtherabbit
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Re: Atari Jaguar csync TTL?
coupling capacitor + attenuation resistor definitely sounds like a better solution than sync stripping the CVBSFBX wrote:Ste from HD Retrovision was kind enough to run scope and spice tests on the Jaguar pin 5B, his results suggest all you need is a series 680 Ohm Resistor and series 220uF capacitor. No need for logic buffers as this should be plenty sufficient.
Re: Atari Jaguar csync TTL?
Just saw this on retro-access.com, if anyone was wondering about their Jag cables:
Additional note: We have received some questions recently about the components used on the c-sync line. We have always wired these cables with a 470 ohm resistor in the Jaguar end and a 220 uf capacitor in the SCART end.
Re: Atari Jaguar csync TTL?
I've had a Retro Access cable since they introduced them and it works great.
Re: Atari Jaguar csync TTL?
It's because 470 is MUCH better than nothing, however, 680 is optimal. I had sent Rachel this information, but she didn't seem to trust me on it.strygo wrote:I've had a Retro Access cable since they introduced them and it works great.
Re: Atari Jaguar csync TTL?
Sounds like the Retro Access sync-on-luma cable is the best and safest option currently available from either seller.
Re: Atari Jaguar csync TTL?
We talked some more and she said she's started using 680 Ohms now. Although to be fair, 470 was likely 'safe enough'. It's just that 680 is optimal.copy wrote:Sounds like the Retro Access sync-on-luma cable is the best and safest option currently available from either seller.
Re: Atari Jaguar csync TTL?
Nice!FBX wrote:We talked some more and she said she's started using 680 Ohms now. Although to be fair, 470 was likely 'safe enough'. It's just that 680 is optimal.
Re: Atari Jaguar csync TTL?
Hi, sorry to resurrect this thread but I am in a sorry position that something has caused my Gscartsw_lite to die, it would appear that my Altera IC is beyond repair (been communicating with superg to try and get to the bottom of the issue).
All my cables are from retrogaming cables, apart from one which is for my NESRGB (just a straight through din to scart).
I have a Jaguar and one of the original Jag scart cables from retrogamingcables. I am trying to work out what killed the Gscartsw. Could the issues discussed in this thread have been a contributory factor?
All my cables are from retrogaming cables, apart from one which is for my NESRGB (just a straight through din to scart).
I have a Jaguar and one of the original Jag scart cables from retrogamingcables. I am trying to work out what killed the Gscartsw. Could the issues discussed in this thread have been a contributory factor?