metso Model PDP Series PDP401

Distributed Processing Unit Functionality

The Model PDP Distributed Processing Unit (DPU), which runs under the

Windows CE.net real-time multitasking operating system, is the hardware

processing engine of the maxDNA distributed control system. The DPU

performs primary data acquisition, control, and data processing functions.

The DPU, also known as maxDPU4F, is a self-contained microprocessor

based, rack-mounted unit, which occupies a single slot in a Remote

Processing Unit cabinet using an 8-wide maxPAC backplane. It is designed

to operate with user-defined combinations of maxDNA Model IOP

Input/Output Modules, and to communicate with other devices, such as

Programmable Logic Controllers and Remote Terminal Units.

As a station on maxNET, the DPU scans and processes information for use

by other devices in the maxDNA system. Each DPU performs:

• Comprehensive alarming and calculations.

• Logging of Sequence of Events (SOE) data at 1 millisecond resolution.

• Acquisition of trend information.

• Continuous scanning of Model IOP I/O modules.

• Execution of predefined algorithms, called Function Blocks, for process

control and data acquisition.

Model Numbers

Model PDP401 – DPU4F #181550

Model PDP403 – DPU4F #181550. Backup Cable #050292

Model PDP406 – DPU4F w/IRIG & Comm. #181551

Model PDP408 – DPU4F w/IRIG & Comm #181551. Backup Cable

#050292

Distributed Processing Unit Hardware

A DPU consists of a printed circuit board containing the Control Processor

and Input/Output Processor (IOP) and is installed in a maxPAC chassis. The

DPU’s front panel contains status LEDs, a MODE Switch, Backup

Connector, Network Connectors, and takeover and reset buttons.  An

optional assembly also contains a Serial Port Connector for interface to PLCs

and a BNC Connector for interface to an IRIG-B time source. See “Front

Panel Controls and Features,” later in this chapter.

Control Processor

The DPU is comprised of a single printed circuit board that contains a

Pentium class Control Processor and a dedicated micro-controller for

scanning I/O. There are also sockets on the board for 64 Mbytes of

CompactFlash and 128 Mbytes of DRAM.

Performance

A multi-speed processing system is built into the maxDPU4F, which allows

objects to be executed in three different time classes. From as fast as 10 msec

to 1/2 second. Up to 8.500 control objects (Function Blocks)can be executed

in the DPU. Note also that Function Blocks can be combined to create

libraries of Standard and Custom Blocks. A Function Block can be as small

as an Atomic Block, such as an AND or OR gate.

A data point management system (DPMS) keeps track of the object size and

the total execution time for each time class.

I/O Bus Interface

A Motorola 68332 32-bit I/O processor and field programmable gate array

(FPGA) are used to interface to both the Model IOP I/O bus and to the I/O

Bus Expander Module (BEM) for remote I/O applications. Up to 60 Model

IOP I/O modules can reside on each electrical bus. See Publication 278596.

maxPAC Hardware Reference Guide, and for earlier Model 564 I/O, see

278563. Model IOP I/O System Installation and Preparation. The maximum

length of the Model 564 I/O bus is 30 ft. The length of the remote I/O link

with fiber optic extenders is up to 2000 m.

Fully Self Describing Object Oriented Database

All information regarding the operation of the DPU is kept in DPU memory,

including: tag names, descriptions, tuning constants, alarm limits, etc. In

addition, all graphical configuration data (sheet number, object location,

wiring) is stored in the DPU.

This means that there is no possibility that the configuration observed is

different than that which is installed in the DPU.

Objects are stored in a fully hierarchical database, allowing for easy cut and

paste changes and protection of control strategies.

Fully Software Backplane Compliant

With the software backplane installed, the DPU can access any exposed data

stored anywhere in a connected system as long as the connected system also

uses the SPB Protocol. Peer-to-peer transfers are rapid and transparent. No

independent transfer agent is required.

The Software Backplane uses subscription services where data is only

transmitted when changes are detected.

Sequence of Events

Each DPU includes a built-in Sequence-of-Events (SOE) recorder that can

monitor up to 512 discrete inputs. These inputs are scanned 1.000 times a

second and state changes are time stamped with 1 ms resolution and stored in

the DPU’s 10.000-event buffer. Each input has a separately configurable

digital filter for contact debounce.

Distributed Processing Unit Specifications

Operating temperature range

Storage temperature range

Relative humidity range

Power requirements

Current:

Powering the DPU

0 to 60 degrees C

(-)25 to 70 degrees C

5 to 90% noncondensing

24 Vdc ±4 Vdc

0.9 A @ 24 Vdc

The DPU operates from the main redundant 24 Vdc power supply system in

the maxDNA system cabinets.

Mounting the DPU

The DPU is mounted on the Input/Output (I/O) backplane with maxPAC and

earlier Model 564 Input/Output modules.

Positioning the DPU in a Standard maxPAC Chassis

The DPU must be mounted in the left most position of the Model IOP rack to

allow for the best airflow. The Backup cable and Ethernet communications