Links

For more Information on MOSCAD please
refer
1) http://www.moscad.com/
2) Moscad System Planner

Dual Power Source

The MOSCAD RTU uses a dual source of operating power. The primary power source is a power supply
connected to the ac power mains. The primary power source provides a nominal 12 Vdc operating voltage to the
modules, the communication device, and to other active elements within the RTU. A rechargable battery is also
present that will power the modules, communication device, and certain other active elements of the RTU when
ac main power fails. The battery is connected to these elements through the power supply; the power supply acts
as the battery charger. The power supply/battery interface provides zero-transfer-transient performance.
Low-current and high-current power supplies are available. The low-current power supply provides 3 amps
at 12 Vdc and is included in MOSCAD RTU models that have no radio or low-power radios. The high-current
power supply provides 8 amps at 12 Vdc and is included in MOSCAD RTUs with high-power radios or in the
model with an interface to an external radio. The V261 option will replace the 3 amp power supply with it’s 8
amp equivalent when the extra current capacity is needed. The V274 option replaces the power supply and battery
with a cable that may be connected to a clean external source of 12 Vdc power; the V251 option changes the
input voltage from 117 Vac 50/60 Hz to 230 Vac 50/60 Hz.
The battery capacity is 5 A-h and is recharged by the power supply. The V326 option adds a second battery
to achieve 10 A-h capacity. Battery life is dependent upon transmitter usage, etc; refer to Chapter 3 for a discussion
of current drain & battery life. A lithium battery is also provided in the CPU module that is active only when ac main power fails and the backup battery disconnects. The lithium battery keeps the RAM and real-time clock
circuits functioning to help achieve an effortless RTU restart following voltage reconnect.
The power supply contains a low voltage disconnect circuit that prevents the battery from an over-discharge
condition which would destroy the battery. If a disconnect should occur following an ac power failure, the power
supply will maintain the disconnect state following power restoration until a minimum level of battery recharge
has occurred (provide the full output of the power supply to the battery). The power supply provides an ac fail
signal to the CPU module; this signal may initiate an ac fail message to be sent to the SCADA Manager and may
cause some RTU startup activities to occur following reconnect.
The CPU module and the rackmount Expansion module both contain a 5 volt power source that can supply
up to 2 amps to the 1-to-15 I/O modules in the module rack. Refer to Appendix A for help in calculating the
current drain from the 5 volt supply.

Multiple CPU Modules

The standard RTU contains a single CPU module that controls all activities in the RTU. Some critical sites
may require a spare CPU module that is seamlessly activated should a failure be detected. The MOSCAD RTU
provides a Dual CPU module mode of operation: the normal CPU module is installed in the left-most position
in a standard motherboard and a second CPU module installed in the immediately adjacent position; eachmodule
is downloaded with essentially identical application programs. In the normal state the second CPU module is
off-line (connected to the I/O modules but not controlling them). The active CPU module periodically sends an
I’m OK message to the secondary CPU module; if the secondary CPU module ever fails to receive the I’m OK
message within the allotted time, it will assume control of the I/O modules and begin all communication tasks.
The RTUmay, following such a switch, send an advisory message to the SCADA Manager or elsewhere to notify
Maintenance that a service call is required.
There are other times when multiple CPU modules are required within a single RTU. The number of required
RS-232 connections may exceed what a single CPU module may support, the amount of data through the several
RS-232 connections may place an excessive time-burden upon a single CPU module, or multiple radios and/or
wirelines may need to be connected to the RTU. Multiple CPU modules are clearly a solution: the CPUs may be
interconnected via the RS-485 2-wire multidrop ports and exchange data using the MDLC protocol’s store-&-
forward capability. The rackmount configuration is the recommended approach: special motherboards are
available that allow multipleCPUmodules with oneCPUcollecting data from associated I/O modules and sharing
that data with the other CPU modules. Refer to the rackmount discussion in the Physical Configuration section
for more details.
The RS-232 Multiplexer (Mux) is available to expand a single full RS-232 port on the CPU module to four
ports. The Mux obtains operating power from the power supply/battery and may be installed within the standard
NEMA configuration or in the rackmount configuration but not in the small NEMA configuration (no space for
the Mux). The Mux operates under the control of Port 2 (or Port 3 when an Async interface is present) on the
CPU module and may be set for broadcast CPU-to-device with first-come-first-served response or set for directed
CPU-to-device input/output; the Mux may also be set to echo characters received from some device back to the
device. All connected devices must support the RTS/CTS/DTR mode of operation.

Communications Interface

Each MOSCAD RTU is identified by the communication device it contains, normally the type and power
level of the internal two-way radio device. The CPU module in the RTU contains the communication interface
board most commonly used with the included radio although
other types of interface boards may generally be
substituted.
Wireline communications may replace radio communications.
Two separate pieces of hardware are added
to the RTU: a line interface plug-in board (internal modem)
in the CPU module that replaces the radio interface
board and a line interface box that replaces the radio. It is
mechanically impossible for simultaneous radio and wireline
communications to exist in one CPU module (except
for the special case when an external modem is connected
to Port 2 and some radio interface exists on Port 3).

CPU Module

The MOSCAD CPU module contains the majority of the product’s intelligence. It has a Motorola 68302
16/32-bit CMOS processor, RAM, ROM, and Flash memory, lithium backup battery, a real-time clock, plus the
interfaces to the I/O and communication aspects of the RTU. The
CPU module may be programmed, using the Programming Tool-
Box, providing it with the capabilities expected of a PLC.
Three different CPU modules are available:
» The Series 300 CPU module contains a versatile memory management
system that accepts the download (see Figure 25) of
ModBus and other third-party protocol drivers and compiled ‘C’
functions as created by the user; it is the CPU module included
with all MOSCAD RTUs.
» The Series 200 CPU module (V424 option) contains a bit less
total memory and a memory management system that does not
accept the download of ‘C’ functions, ModBus drivers, etc. The
Series 200 CPU may be used in the RTU when these download
functions are not required and when the application program and
in-module data storage requirements are small.
» The Series 400 CPU module (V426 option) uses Flash memory
instead of EPROMs: upgrades to the operating system are easily
downloaded into the Flash memory, and more Flash memory is
available than on the Series 300 CPU module to store larger
compressed source code files
The Series 400 CPU accepts the download of ModBus and other drivers, of compiled ‘C’ functions,
etc; it must be used in Europe for compliance with the standards on emissions and magnetic susceptability.
An additional 1.2 Mbyte of RAM (V449 option) or amath coprocessor (V445 option) or both (V446 option)
may be added to any CPU module; the RAM addition is recommended when large amounts of collected or
calculated data is to be stored within the CPU module, and the math coprocessor addition is recommended
whenever the application requires math-intensive operations, i.e. AGA8, etc.
A real-time clock chip is located on the CPU module and provides year (including leap year), month, day,
date, hour, minute, second, and milliseconds support to the application. Diagnostic or error messages contain the
time of the occurence; input events may be time-tagged; time-sensitive application tasks may be created. The
clocks within the RTUs may be synchronized by a manual time download from the ToolBox, an automatic time
download from the SCADA Manager, or via an automatic message from another RTU having a GPS receiver.
Each CPU module contains three data ports with different capabilities.
» Port 1 provides either RS-485 (2-wire multidrop) or a partial RS-232 (data but no RTS, CTS, DTR, etc.)
communications to other CPU modules, to the Programming ToolBox, or to the SCADA Manager computer
according to the port definition loaded from the ToolBox.
» Port 2 provides a full RS-232 communications and may be configured by the ToolBox as either DTE or DCE
for data connectivity under the control of the loaded application or configured as a system port for local or
remote (dial-in) ToolBox use.
» Port 3 is normally the communications port and contains a plug-in communication interface appropriate to the
medium used; it may also be provided with a second full RS-232 capability when appropriate.
All modules include 20 LEDs that provide information regarding the operation of the module. The LEDs
on the CPU module include the availability of a configuration and application in Flashmemory, communications
with the ports, etc.

MOSCAD RTU

The MOSCAD RTU is a universal device that may serve
as an RTU, a PLC, or as the system FEP. It is placed at the
system’s field sites to collect data from on-site sensors,
add data from off-site sources, and use this data aggregate
to make decisions regarding how some process is operating.
The RTU may make changes to the local process;
messages may be initiated that send data elsewhere to
influence the operation of off-site equipment or to advise
the SCADA Manager of some important change.
The RTU consists of a mounting plate containing a
motherboard, power supply/charger, battery, Series 300
CPU module, communications interface, communications
device (radio or modem), and space for numerous
Input/Output (I/O) modules. The RTU is normally packaged
inside a steel NEMA-4 enclosure although several
options exist to change the size and/or material of the
enclosure or to convert the model to a 19" rackmount
configuration.

MOSCAD System Overview

The purpose of a MOSCADsystem is typically to provide some degree of automatic operation to a new or existing
customer process. The process may be found in water pump stations, sewage lift stations, communication system
monitoring, security, public notification control, electrical substation monitoring, distribution automation,
demand-side management, automated meter reading, or other applications. This automation is provided by a
mixture of hardware.
RTU: The field sites are equipped with MOSCAD
RTUs that collect data from on-site sensors, add data from
off-site sources, and use this data aggregate to make
decisions regarding how the process is operating. Changes
to the local process may be made; messages may be
initiated that send data elsewhere to influence the operation
of off-site equipment or to advise the SCADA Manager
of some important change.
Communications: The multiple sites in the system
may communicate among themselves by utilizing a variety
of communication choices: two-way conventional,
trunked, or MAS radio plus wire-line, fiber, microwave,
and satellite networks. MDLC is the signalling protocol
employed by MOSCAD, is based on the 7-layer OSI
recommendation, and is designed to be totally functional
on all of these communication media.
MDLC includes a store-&-forward capability that
permits different communication media links to be incorporated
into the total system, i.e. conventional radio and
trunked radio and microwave radio and wireline all interconnected
by MOSCAD into a single communication
system. Data may be passed from any site to any other site
in the system (peer-to-peer) either directly or by multiple
hops through intermediate MOSCAD sites. This peer-topeer
communication capability enables system designs
that use a distributed-intelligence operating philosophy;
central-intelligence-only systems may also be implemented
if the load on the communication system permits
it.
FEP: The Front End Processor is used at the central
site(s) to provide a two-way path to the communication system and the distant RTUs from the SCADA Manager
hardware & software. The FEP converts MDLC protocol data from the RTUs to a protocol used by the SCADA
Manager vendor: when the ModBus protocol is used, the FEP will maintain a local database of all the data from
the multiple in-field sites; when TCP/IP is used, the FEP is simply a gateway between the two different protocols.
The FEP always acknowledges all RTU-initiated messages. The FEP also provides a two-way path between the
MOSCAD Programming ToolBox and the field RTUs for those functions unique to MOSCAD that are not provided by the SCADA Manager software (over-the-air programming download, diagnostics upload, more).
SCADA Manager: The SCADA Manager provides the operator with the display and report tools necessary
to view and manage the associated process(es). The SCADA Manager obtains data from the FEP according to
its needs and typically presents that data on custom-created display formats; control messages may also be
initiated from these custom screens. Security is typically implemented via permission levels activated by the
operator’s sign-on password. Microsoft Windows is becoming the operating system of choice because it easily
supports the desired graphic symbols used on the custom screens. The report capability may be provided by the
SCADA software or a data export to Microsoft Excel or equivalent may be utilized. The end result is an easy to
use pictorally-described representation of the field status of key equipment items plus the means to make changes
in how those pieces of equipment operate.