Allen-Bradley A-B QUALITY DL20 Series User Manual page 80

Chapter 7
The Parallel Port
Input Converters
Parallel Port
Sampling Methods
7–8
The parallel input circuit allows inputs to accept DC input voltages from 5 to
30V. An input voltage of 120VAC 60Hz is also accepted if a Parallel Input
Converter (Catalog No. 2706-NG1 or NG2) is installed.
Almost all programmable controller output modules have some leakage
current in the off state. The parallel inputs on the DL20 are designed to
ignore this output leakage current. The Parallel Input Converter is especially
insensitive to the larger levels of leakage current that typically come from
AC output modules.
ATTENTION: The Parallel Input Converters (Catalog No.
2706-NG1 or 2706-NG2) cannot accept 220/240 VAC.
!
If 220/240 VAC is applied, damage to the Parallel Input
Converter will occur.
The DL20 can read data on the parallel port two different ways:
Time-Driven Sampling
Reads the parallel port periodically.
Event-Driven Sampling
Reads the parallel port whenever a transition occurs on the edge triggered
strobe (ETS) input (terminals 10 and 11). This method is slightly more
difficult to implement with a programmable controller's discrete I/O than
time-driven sampling, however it may allow slightly faster input.
Choose the method most suitable to your application using the Set Up I/O
Ports special function as described in Chapter 8.