Sierra Video Tahoe Series 16 - Manual (Page 54)

Sierra Video Systems
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data inputs to the 504045 is in series with a 4.7K resistor. This serves two functions. It
protects the logic circuits on the 504045 CMOS inputs from static over voltage or static
damage. Second, it protects the bus in the system from a failure on an individual 504045
module.
U6 is a 4 line to 16 line decoder. Its output determines which bus on the 504045 is being
addressed by the central controller. The strobe input (J1-6S) is centered timing wise in
the data time that appears on the other logic lines to the 504045.
Power Supply
Low voltage AC enters the 504045 on J3 pins 27 and 28. If dual supplies are used, low
voltage AC from the second supply enters the 504045 on J3 pins 25 and 26. The low
voltage AC is rectified (D1 through D8) and filtered (C1 and C2) to unregulated DC. U10
provides +5VDC for the logic circuits and switching array. U11 provides -5VDC for the
switching array. U12 is a 78M15 and provides +15VDC to the analog circuits. U13 is a
79M15 and provides -15VDC to the analog circuits.