Rockwell Automation 2706 DL20 SERIES G USER MANUAL - Manual (Page 74)

Chapter 7
The Parallel Port
7–2
Figure 7.2 illustrates a typical example of using discrete I/O outputs with the
DL20 parallel port:
Figure 7.2
Using Discrete Outputs With the Parallel Port
+
-
D9 D8 D7 D6 D5 D4 D3 D2 D1 D9 MS0 MS1 GND
11A 11B 12 13 14 15 16 17 18 19 21 20 23
Terminal
Number
Terminal Block
Designation
Power Supply
5-30 VDC
(Observe DC
Polarity)
PC Outputs (12)
DL20 Parallel Port
Logic Levels
Data line D0 can have a value of either 0 (ground level) or 1 (voltage
present). The convention of having voltage representing a 1 and ground
representing a 0, is known as positive logic. The opposite convention is
known as negative logic. The DL20 can accept either.
Each parallel input understands two voltage levels: On or Off. There is also
an indeterminate state when the voltage level is between On and Off.
Table 7.A shows the voltage levels and their logic values for input terminals
D0-D9 and strobe lines MS0 and MS1.
Using the Parallel Port