7700 Multiframe Manual
7725DSK-LG / 7725DSK-LG-HD HD/SD Logo Inserter & Media Keyer
Page 2-8 Revision 1.4 INSTALLATION
10/100: This LED is ON when a 100Base-TX link is last detected. The LED is OFF when a
10Base-T link is last detected. Upon power-up the LED is OFF as the last detected rate is
not known and therefore defaults to the 10Base-T state until rate detection is completed.
LN/ACT: This dual purpose Green LED indicates that the 7725DSK-LG has established a valid
linkage to its hub, and whether the 7725DSK-LG is sending or receiving data. This LED
will be ON when the 7725DSK-LG has established a good link to its supporting hub. This
gives you a good indication that the segment is wired correctly. The LED will BLINK when
the 7725DSK-LG is sending or receiving data. The LED will be OFF if there is no valid
connection.
2.8. CONNECTING THE GENERAL PURPOSE INPUTS AND OUTPUTS
Figure 2-2 shows a simplified schematic diagram of the GPIO circuitry. The user can connect GP+3.3V
supplied from the keyer unit into the Vext pin to provide power to the GPIO opto-isolator circuitry. In
this configuration the user can activate GPIs simply by connecting the GPI input pins to Ground (see
Figure 2-3). This can be done with a button, switch, relay or an open collector transistor. In this
configuration the GPOs will be internally pulled up to 3.3 volts (see Figure 2-5). 3.3 volts is available to
the user to be used for driving external circuitry. Care must be taken to limit the load to 0.5W ensuring
that there is no affect on the power supply source on the unit.
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Warning: Do not connect GP+3.3V from one unit to another unit’s GP+3.3V
output.
Alternately, the user can connect an external power source for the opto-isolator circuitry. The Vext
voltage must be greater than the voltage supplied to GPI by at least 3v. Figure 2-4 and Figure 2-6
show how to wire the GPIs and GPOs from an external power supply.
The tally outputs are active low with an internal pull up (10k Ohm) resistor to the Vext pin. When active,
the output will go low and is able to sink up to 10mA. When inactive, the signal will go high (to the
voltage applied to the Vext pin). Do not attempt to source more than 100µA from the output.
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