cine monitor watchdog

As i've been hacking on the adapter, I came up with a simple
watchdog circuit that could be retrofitted on a cine monitor.
It's pretty simple, you put tri-state buffers in line with
the DAC data and a little 555 timer reset by the "initialize
switch" line. If you stop getting "initalize switch" pulses
either your CPU is dead, or the monitor is unplugged, and
you tristate the buffers. on the DAC side, there is one pull
up and 11 pull-down resistors on each DAC which pulls the
DACs to the center of the screen..

BTW, it turns out the inputs to the X and Y register MSB's
are inverted, so 0,0 in becomes 0x800, 0x800 to the DACs
Received on Thu Aug 7 18:20:04 1997