Installation - 2
When used as a digital output (B) the external circuit connected to the output pin can also be TTL, AS, CMOS, HC or a warning light, provided the light has an external bias supply.
When used as isolated pairs (C), each pin pair can be connected to external circuits with the following restrictions: Only adjacent pairs can be used together. Only the even pin of each pair can be programmed to set the logic level as low true or high true. When Low True is programmed, the output is true when the pins are shorted. When High True is programmed, the output is true when the pins are open.
+5V | +5V |
| DIG I/O |
| DIG I/O | |
4.7K | Connector | 4.7K | ||
Connector | ||||
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Dig In signal | Odd or Even Pin |
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A. Digital Input |
| +5V | ||
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| Common | Isolated |
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| Dig Out signal |
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| +5V |
| 4.7K | |
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4.7K
C. Isolated Output
Even Pin
Adjacent Odd Pin
Odd or Even Pin
Common
Dig Out signal
B. Digital Output
Figure 2-3. Equivalent Digital I/O Circuits
The following figure illustrates some typical DIO hardware connections.
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