Feature Spec
www.digi.com
Features/Benets
About the Pass-Through
Port Feature
A serial HMI (or other device) normally connects to a PLC’s
serial port. Adding a device server between the two consumes
the PLC’s serial port leaving no place to connect the HMI.
With the Digi One IAP pass-through feature, the single serial
port on the PLC can be shared – its pass-through port connects
to the HMI while its primary serial port connects to the PLC –
eliminating the need to unplug the serial connection from the
Digi One IAP so that a local serial master can be connected to
the PLC instead.
If your island of automation uses a supported multi-master
protocol (e.g., Modbus/RTU or AB/DF1), the Digi One IAP
allows the existing serial master to continue polling the serial
slave. As the Digi One IAP receives requests from the serial
master, it acts as a proxy to obtain answers from the slave and
transparently return those answers to the serial master in an
understood protocol.
The Digi One IAP’s real magic occurs when a remote network
master (e.g., a SCADA or data warehousing application)
connects. Just like the serial master, the remote master believes
it has sole control of the serial slave. The Digi One IAP manages
the messages from the two masters such that the serial slave is
unaware it has multiple masters. Since the two masters are
competing for the serial bandwidth, each sees the slave as
slightly slower to respond.
If multi-master functionality is not required, the Digi One IAP
can run as a pure two-port device server – supporting two serial
slaves, two serial masters or a serial master-slave pairs –
allowing the host application to communicate with separate
serial devices across the network.
Manufacturers typically have “islands of automation”
throughout their production facilities – a PLC serially linked
to an inspection machine or an HMI panel serially connected
to a PLC. The Digi One IAP running with the “pass-through
port” enabled offers a low-impact way to retrofit such islands
of automation for central access by Ethernet without disrupting
their operation.
Pass-through functionality
Multimaster capabilities
Multi-protocol support
Available on Digi One® IAP
Pass-Through Port
• Easy connections for HMIs and operator panels
• Quick set-up – no need to nd special cables
or the PLC programming port
• Works with Digi’s IA multi-master engine
• Multiple-master devices and systems can
simultaneously access a slave
• Modbus RTU/ASCII, Allen-Bradley DF1,
Omron Hostlink, FINS, Compoway/F
Overview
© 2004-2009 Digi International Inc.
Digi, Digi International, the Digi logo, the Making Wireless M2M Easy logo, Digi One and PortServer are trademarks or registered trademarks of
Digi International Inc. in the United States and other countries worldwide. All other trademarks are the property of their respective owners.
91001233
C1/609
Serial RS-232/422/485 Serial Port 1
Pass-through Port
Digi One® IAP
PLC (Serial Slave)
HMI Panel
(Serial Master)
PanelMate
Programming
Software
22/485
Se
ri
ri
al
l
al
P
P
o
t
or
r
t
t
t
Di
D
g
i
O
n
Ethernet
HMI Software
(Network Master)
Ethernet
PLC
(Serial Slave)
HMI Panel
(Serial Master)
PanelMate
Programming
Software
HMI
Software
Island Of Automation
Diagram 1: Solution Before Pass-Through Port
Diagram 2: Digi Pass-Through Port Solution
Digi One IAP 70001777
Product Part Number