Specifications

www.digikey.com/maxim-industrial 31
Programmable logic controllers (PLCs)
Digital I/O functions
Overview
Digital I/Os interface to industrial
sensors and actuators and communi-
cate with digitized information. The
sensors and actuators are located in
the field and, thus, are represented
on the lowest level of the control
system’s hierarchy. In contrast to
analog I/O modules, digital I/O
modules send or receive digitized
information, which is either 1-bit
(binary) information or quantized
values. The information flow can be
uni- or bidirectional, depending on
the interface type.
There is a significant advantage to
using digitized information: digitized
data is more tolerant of noise. This is
important, because interference on
the programmable-logic-controller
communication link is higher than
typically found with analog commu-
nication. Consequently digital I/O
functions allow longer cable runs at
low data rates.
Interface types
Common digital interfaces are 24V
digital I/Os. The 24V digital interfaces
are unidirectional and based either
on two-, three-, or four-wire cabling.
A 24V digital I/O provides both the
24V and ground supplies to the
sensor/actuator, as well as one or
two (unidirectional) data lines.
IO-Link® is a new sensor/actuator
interface technology based on 24V
I/Os. In an IO-Link system the data
line is bidirectional and supports
data rates up to 230kbps. The IO-Link
point-to-point interface connects
one sensor or actuator to one digital
I/O port. Remote configuration,
diagnostics, and monitoring of the
peripherals is are enabled with intel-
ligent and configurable sensors.
The CompoNet® network uses RS-485
differential signaling to commu-
nicate with sensors and actuators
at high data rates. A master-slave
network, CompoNet allows one
master to control up to 384 slaves.
Optional 24V powering of up to 5A
is allowed over the same cable. The
sensors and actuators are typically
powered by a 24V supply, which is
isolated from the system’s backplane.
This function is shown on the block
diagram in the Isolated power-supply
functions section below.
Digital I/O functions
With an industrial digital I/O interface, 1-bit or quantized data flow to and from the sensors and actuators is easy.
For a list of Maxim's recommended PLC solutions, please go to: www.maxim-ic.com/plc.
TO/FROM
SENSORS,
ACTUATORS,
HMI
SWITCH
DEBOUNCER
VOLTAGE MONITORS
HOT-SWAP
CONTROLLER
ISOLATED POWER SUPPLY
DIGITAL INPUTS
IO-Link
RS-485
CompoNet
DIGITAL OUTPUTS
CONTROLLER
UART
CAN
WIRELESS
THERMAL
MANAGEMENT
POWER-LINE
COMMUNICATIONS
COMPARATORS
= MAXIM SOLUTION