© National Instruments Corporation 5-1 PC-OPDIO-16 User Manual
Chapter 5Theory of Operation

This chapter describes the theory of operation for optically isolated digital I/O on the

PC-OPDIO-16. This chapter also discusses using NI-DAQ functions with the PC-OPDIO-16

board.

Functional Overview

The block diagram in Figure 5-1 shows a functional overview of the PC-OPDIO-16.

PC I/O Channel
Data/
Address
Control Plug and Play
Interface
PC I/O
Channel
Interface
Address
Select and
Control
Control
82C55A
Digital
I/O
Control
+5 V
1A Fuse
A<0..1>
PA7
PA0
PB0
PB7
TLP121
TLP121
LDA210
LDA210
Back Panel Connector
•
•
•
•
•
••
•
•
•
•
•
VCCO0
VOUT0
COM0
VIN7
IGND7
+5 V
DGND
Data
D<0..7>

Figure 5-1. PC-OPDIO-16 Block Diagram

The following are the major components making up your PC-OPDIO-16 board:

• I/O channel interface circuitry

• Digital I/O circuitry

• Optical isolation circuitry