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.