Re: Cinematronics XY characteristics

At 09:14 AM 5/6/97 -0400, you wrote:
>> You'll also need some circuitry to switch between the different type
>> monitors used: 2 level, 16 level, 64 level, and Color.
>
>Zonn,
>
>How do the inputs look for the 16-level, 64-level, and (especially) the
>color versions?
>
>The way I understand the 2 level, one of the two inputs indicates beam
>on or off, and the other one makes the beam brighter if its on. Is this
>correct? What would happen if the bright signal was on but the beam
>signal was off? The circuit (from 20,000ft) looks like either input
>being on would turn the beam on to the low level. Is that right?

That would be the case if you were to twiddle with the bits going into the
monitor. On the CPU card the Brightness level is gated with the Trace
On/Off signal to prevent a "Brightness without Trace" state from ever
getting to the monitor. This gating can be disabled to allow the Brightness
signal to pass unobstructed to the monitor, that's what the Norm/Var jumper
on the CPU card does.

>Do the 16- and 64-level versions work similarly (on signal for on/off,
>and 4 or 6 bits for intensity)? How are the color inputs arranged?
>
>I've been looking at laying out a circuit to handle the 12-bit
>deflection signals, but I'm not sure how to handle the brightness
>signals.

They all have one thing in common. They share the X DAC's data lines, and
they then use what was the brightness line as a strobe line.

So to set a color or intensity the software places the color or intensity in
the A register, executes a 'VIN' (Vector Initialize) instruction which
latches the data onto the X DAC's data bus. The Brightness line (which is
normally set to bright, and is mapped to the instruction 'OUT 6' is then
strobed to normal, then back to bright. At this point, since you've also
moved the CRT beam off in some random direction and have placed some random
load on the Yoke amplifiers, they re-center the beam with another VIN
instruction.

The above sequence is used for all the multi-level intensity games.

The following is off the top of my head since I don't have any documentation
here at work:

As far as mapping goes, the 16 level display uses the 4 lower bits of the 12
bits going to the X-DAC (bits 3-0), and I believe they use inverted logic.
'0' being maximum brightness. The 64 level display uses bits 7-2 and it's
logic is opposite that of the 16 level display.

The Color Card didn't have a schematic, so I sat down with a ohm meter and
traced the color latches through to the 4 bit DACs leading to the RGB op-amp
buffers, to determine which bits were which color, and all the signal
inversions leading up to the CRT guns. The Color Monitor uses all 12 bits:
Bits 11-8 are the Blue level, Bits 7-4 are the Green level, and Bits 3-0 are
the Red level. All the signals are inverted so the value 0x000 gives a
maximum brightness of WHITE.

Before you go laying all this out onto a PCB let me double check all this! ;^)

Your also going to need to know a little more about the offsets. 0,0 is not
the center of the X,Y display. It instead refers to the lower left corner
of a 1024x768 display.

-Zonn
Received on Tue May 6 10:21:02 1997