Re: Tailgunner has a special monitor?

At 09:37 AM 8/11/97 -0500, you wrote:
>> I was just trying to figure out where the XDAC output signal for the
>> comparitors used for the joystick A/D is generated, and I don't see
>> pin 16 of the monitor connector hooked up to anything on any of the
>> monitor schematics that I have (I don't have a Tailgunner manual..)
>> Could someone take a look and tell me how it is interfaced (I assume
>> it's somewhere between the DAC output and the analog switches, but
>> is there a buffer or anything used to isolate the off-card signal
>> from the analog switches?)
>>
>> I was also curious what kind of Cine monitor Tailgunner uses.
>
>I thought that was standard. The motherboard pattent actually talks about
>how to use this along with the JUMP-EXTERNAL instruction to get analog
>inputs. I assumed this means the signal is present from all CineMonitors.
>I'm sure I've seen what you're looking for, but I don't have it in front
>of me right now. Funny how they decided ahead of time to route the
>X-Position to the sound board via the motherboard!
>
>BTW, Tail Gunner was the only game to use JUMP EXTERNAL. Space War uses
>it as an unconditional jump and all the other games have it wired to
>the sign bit so it's Jump Minus (JMI). Uhhh Zonn what does Speed Freak
>do with it? I still can't make that run without locking up :-)

I'm a little confused about the "unconditional jump" use in Space War.

A read once (on RGVAC) that you found this to be the case, but I couldn't
find the jump used anywere in the code. I placed breakpoints in my emulator
on the jump external instruction, and I never found it. I then burned some
Space War ROMs and place them in an unmodified Star Castle board and they
ran just fine.

Also looking at the schematic, the external input is not pulled hi or low.
Though TTL usually pulls itself high if left floating, this seems like a
pretty risky thing to be basing the game code on -- though it might be
pulled high on the sound board, I didn't check.

The version of Space War I was using was from a Vectorbeam, not
Cinematronics. It makes me wonder if Cinematronics changed the real jump
unconditional instructions to the jump on external input, to distinguish the
code from Vectorbeam's. I assume they would add a jumper on the sound board
to pull this input high all the time, if this were not already being done.

The biggest problem I see from people that have tried running Space War on a
Star Castle (or whatever board) is they don't check to make sure DIP
switches 3 through 7 are turned off. Space War uses these switches as
inputs from the control panel and turning these on causes some (appearently)
unpredictable behaviour.

As for Speed Freak, It doesn't seem to matter as to the state of the JMI, so
I assume it doesn't use this instruction either.

-Zonn
Received on Mon Aug 11 10:40:21 1997