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Institute Mihailo Pupin
Institute Mihailo Pupin is the leading Serbian R&D institution in the field of Information & Communication Techologies.

Automation & Control Systems Ltd
The Automation & Control Systems Ltd is the core division of the Institute Mihailo Pupin, and the owner of the projects: ATLAS Systems and ATLAS-MAX.

The long list of the Institute's references and customers is the best proof of its high professional and techological achievments.

The other related IMP project: VIEW4 Software Package for control of complex processes

You are here:     ATLAS-MAX System Organization Hardware Organization ATLAS PI Bus


All ATLAS Process Interface I/O modules fully comply with the proprietary ATLAS PI Bus standard, which specifies types, modes of operation, and locations of all address, data, control, identification and other process interface signals.  All PI modules are 6HE sized PCBs with the rear 64/96 pin DIN connector toward ATLAS PI Bus back-panel board.  Connections with the process and introduction of raw process signals to PI modules are accomplished via other connectors (typically front-end connectors), which are physically dislocated and galvanic-separated from the ATLAS PI Bus.  The ATLAS PI Bus signal layout is:



The ATLAS PI bus is strictly internal rack bus, realized as a rack backplane board within the PI racks (enclosures).  In that way, the bus is fully protected against external electrical and magnetic interferences (EMI), simply by shielding the rack itself.  ATLAS PI Bus signals control is alternatively provided in one of the following two ways:

ATP02 PI Rack

ATLAS PI Bus implementation with ATP02 Bus Controller


XP2 PI Rack

ATLAS PI Bus implementation with XP2 Microcomputer


While the XP2 controlled ATLAS PI Bus presents a single-rack self-containing microcomputer device (and consequently is easy to understand), the ATP control presents a more complex, but also a more powerful approach.  The following block diagram explains that in more details:

PTA-ATP Control Block Diagram

External connections with PI racks are accomplished by PTA-ATP shielded cables with twisted wires.  Each signal is led differentially through a twisted wire pair, providing a maximum protection against EMI interferences.  If multiple PI racks are required, they are daisy chained up to the required PI size and capacity.

PTA-ATP Layout


The required signal conversions and signals multiplexing are provided by two bus controllers:

  •  Process Interface Signal Controller (Gateway) - PTA02

This gateway module is a part of the Central Computing Unit ATLAS-CPU, and it works in pair with the PI Bus Controller ATP02 (located in the PI rack).  It generates needed address, data and control signals to manage PI modules, which are multiplexed and transferred differentially toward distant PI modules:


PTA Signals


  • Process Interface Bus Controller - ATP02

This Bus Controller is a part of the PI rack and directly manages PI modules in the PI rack.  The module works in pair with the PI Signal Controller PTA02, and converts and multiplex address, data and control signals on the ATLAS PI Bus.  The signal transfer is provided differentially toward distant ATLAS CCU unit.  Two 50-pins connectors (labelled as “INPUT” and “OUTPUT”) enable inter-module daisy-chain connections.  


ATP Signals


Note: Two implemented proprietary standards are guarantors for a reliable functioning of ATLAS Process Interface in the harshest EMI environment.  All critical bus elements are shielded and proceeded differentially.