S
SixteenThirtytwo
- Jan 1, 1970
- 0
I'm trying to design a video output board for my Mega STe computer
which has two different video modes (low/medium resolution colour &
high resolution monochrome) designed for Atari's own colour or
monochrome monitors.
My circuit will allow for TVs and standard VGA monitors as well.
Here's my schematic (drawn with Eagle):
http://img170.imageshack.us/img170/5139/vgaextraswitchesnn2.gif
The normal way the computer determined its display mode is by
"sensing" which monitor is connected to it via its 13 pin DIN
connector. An Atari colour monitor, a TV (it has an RF output) or
nothing connected at all sets it to colour mode.
If an Atari monochrome monitor is inserted into the 13 pin connector
it senses this and sets the computer to mono mode. It does this
because Atari mono monitors have pins 4 (mono detect) and 13 (ground)
connected together internally.
So in order to bypass this I've created a circuit where I change modes
manually with a switch (6 pole double throw(6P2T) , though a 4P2T
would do if I didn't want the LEDs). By utilizing specific connectors
for the specific modes I'm also ensuring that none of the monitors or
TVs will go up in smoke because they're receiving sync rates they
can't handle.
The challenge comes to the part concerning use of Atari monitors.
A mono monitor will set the computer to mono mode by itself (because
of the mentioned pins 4+13 connection) which is fine, but it won't
prevent any TV from being fried if already connected to the SCART
(Euro-connector) or composite out.
An Atari colour monitor however is worse off, because the computer has
no way of sensing this, and if the switch is set to "mono" I could
very well fry it.
So I have the following idea:
I need to have the circuit separate the Atari monitors and VGA/TV/
composite outputs. Since I haven't found any 13-pin DIN connectors
with a built-in switch someone suggested that I modify a connector by
adding a micro-switch to it. That way, by just inserting a 13 pin DIN
plug into the PCB socket the switch status would change and could
control some other circuitry.
The rest of the circuitry (which I haven't figured out yet and need
help with) would:
a) bypass the manual switch (i.e. don't care what mode it is set on,
but set the computer to whatever mode the Atari monitor in question
demands)
b) turn off or direct the sync rates appropriate for the rest of the
outputs (VGA monitor, TV and composite output) depending on which mode
the computer is set to.
Any suggestions to a suitable circuit for this?
which has two different video modes (low/medium resolution colour &
high resolution monochrome) designed for Atari's own colour or
monochrome monitors.
My circuit will allow for TVs and standard VGA monitors as well.
Here's my schematic (drawn with Eagle):
http://img170.imageshack.us/img170/5139/vgaextraswitchesnn2.gif
The normal way the computer determined its display mode is by
"sensing" which monitor is connected to it via its 13 pin DIN
connector. An Atari colour monitor, a TV (it has an RF output) or
nothing connected at all sets it to colour mode.
If an Atari monochrome monitor is inserted into the 13 pin connector
it senses this and sets the computer to mono mode. It does this
because Atari mono monitors have pins 4 (mono detect) and 13 (ground)
connected together internally.
So in order to bypass this I've created a circuit where I change modes
manually with a switch (6 pole double throw(6P2T) , though a 4P2T
would do if I didn't want the LEDs). By utilizing specific connectors
for the specific modes I'm also ensuring that none of the monitors or
TVs will go up in smoke because they're receiving sync rates they
can't handle.
The challenge comes to the part concerning use of Atari monitors.
A mono monitor will set the computer to mono mode by itself (because
of the mentioned pins 4+13 connection) which is fine, but it won't
prevent any TV from being fried if already connected to the SCART
(Euro-connector) or composite out.
An Atari colour monitor however is worse off, because the computer has
no way of sensing this, and if the switch is set to "mono" I could
very well fry it.
So I have the following idea:
I need to have the circuit separate the Atari monitors and VGA/TV/
composite outputs. Since I haven't found any 13-pin DIN connectors
with a built-in switch someone suggested that I modify a connector by
adding a micro-switch to it. That way, by just inserting a 13 pin DIN
plug into the PCB socket the switch status would change and could
control some other circuitry.
The rest of the circuitry (which I haven't figured out yet and need
help with) would:
a) bypass the manual switch (i.e. don't care what mode it is set on,
but set the computer to whatever mode the Atari monitor in question
demands)
b) turn off or direct the sync rates appropriate for the rest of the
outputs (VGA monitor, TV and composite output) depending on which mode
the computer is set to.
Any suggestions to a suitable circuit for this?