Grass Valley 8990ARC v.3.0 - Manual (Page 11)

8990ARC Instruction Manual 11
Installation
GPI Control
The GPI control input at BNCs J7 or J8 (not both) on the rear panel is a
loop-through input to an A/D converter and a 1.21 K
Ω resistor to +5 V.
When the module’s GPI function is enabled, the 8990ARC software will
recognize a GPI input voltage level to select one of four stored user-defined
modes. Looping the input to additional modules allows a single GPI signal
to set them all (up to 10 modules).
The GPI input is created by the application of a parallel resistor between
the coax center and common ground that results in a voltage lower than
+5 V to the A/D converter.
The following voltages (all ±0.4 V) will select the GPI register indicated:
• 1.25 V = GPI 1
• 2.08 V = GPI 2
• 2.92 V = GPI 3
• 3.75 V = GPI 4
The resistors required for these voltages are shown in Figure 4 .
Figure 4. Typical GPI Input Circuit Diagram
1
2
3
4
402 Ω
Open
845 Ω
1690 Ω
3570 Ω
Connects to
J7 or J8
8036_07
Note:
Resistor tolerance = 1%
Only one GPI input can be used