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4-6
Cabling and Wiring
Powering up the computer or asserting the PC bus RESET line clears the
Relay Output register, de-energizing all relays. This event provides a
defined state at power up. A soft boot of the computer ([Ctrl] + [Alt] +
[Delete]) does not produce a hardware reset of the PDISO-8; thus, the
state of the relays is unchanged by soft booting the computer.
Using Isolated Control Inputs
The PDISO-8 contains eight identical opto-isolated control input
channels. The equivalent circuit of a channel is shown in Figure 4-6. Note
that the input is first routed through a bridge rectifier, so that the
connections are not polarity sensitive whether used on AC or DC
voltages.
Figure 4-6. Equivalent Circuit of an Isolated Control Input
R1
470
Ω
Non-Polarity
Sensitive
+5 V
R2
3.3 k
Ω
R3
47
S1
Response
CMOS
Schmitt
Buffer
Data
Bus
CMOS
Schmitt
Buffer
C1
0.1 µF
Isolated Input