Specifications

Copyright © AMETEK
19
19.1 Description
The Party Line Data (PLD) Module provides
“multi-drop” RS-232 data communications over a
single DS0 channel. It occupies one physical slot
in the FOCUS chassis. The module’s interface has
a single DB9 female connector (DCE) for directly
connecting your RS-232 device. The PLD system
does not support hardware handshaking. If hand-
shaking is required, RS-232 channel modules
(232) must be used.
The PLD is designed for use in a variety of
Remote Terminal Unit (RTU) applications. An
example of a SCADA Master/RTU is shown in
Fig. 19-1. In this example, the addressing is a
function of the SCADA system; hence the PLDs
will be set to external address mode.
The PLD’s most prominent feature is its address-
ability. This feature lets you send a message from
the master, or control, unit attached to the “head”
PLD module (see Fig. 19-2) to a specific PLD
module and its attached RS-232 device in a multi-
drop network. In either mode, data passes
transparently through the other PLD modules in
the network. Because only one PLD module (and
it’s attached device) is communicating with the
head PLD module (or master unit), only one
channel, or time slot, is needed.
Using the FOCUS Configuration Software (FCS),
you can configure the module to operate in either
“internal” or “external” address mode (see the
FCS online help facility: Contents > Channel
Module Configuration Overview > Configuring
the FOCUS Channel Modules > Party Line Data
Module (PLD)…). In internal address mode, the
module communicates directly with a computer or
other RS-232 device at a data rate up to 9600 bps.
In external address mode, the module may be
connected to a variety of RS-232 devices commu-
nicating at 0–9600 bps, which is typical for RTUs.
19.2 Application
As noted above, you can configure Party Line
Data (PLD) Modules for either external or internal
addressing. The basic difference is that with
external addressing, the master unit sends a
message to a remote device using the address of
Figure 19–1.
PLD Application Using External Addressing.
19. Party Line Data (PLD) Module