Basic Unit PM802F and PM803F are belong to ABB Freelance AC 800F control system, which combines the best of DCS and PLC. AC 800F encompasses the wide area from small to medium sized application covering the almost entire spectrum of applications. The AC 800F controller has a modular structure. The CPU is designed as a backplane to which various modules – power supply units, Ethernet and fieldbus modules – can be attached in line

with the application.

The basic unit, PM 802F and respectively PM 803F, cyclically scans signals from the fieldbus

lines via the corresponding fieldbus modules, processes these signals according the application programs installed by the user and sends appropriate signals to the fieldbus actuators via the fieldbus modules.

Controller redundancy can be achieved by using two AC 800F. To ensure quick and smooth

takeover in milliseconds by the secondary AC 800F in case the primary AC 800F fails, a dedicated redundancy communications link through the second Ethernet module makes sure that both AC 800F are always synchronized. All inputs and outputs are designed to support redundant operation.

Data communication between AC 700F, AC 800F, the engineering and operator stations runs

via the control network. Engineering station communications can involve new or updated configuration files being downloaded to the controller, or information about the connected modules being reported back. When fieldbus modules are installed or exchanged, the required configuration information is automatically updated.

Configuration and real-time process data is stored in the controllers. To safeguard this data in case of power loss, the RAM power is backed up with batteries located either on the Ethernet modules or on battery modules.

As the basic unit, what’s the difference between PM802F and PM803F?

In conclusion:

The PM 803F has more memory than the PM 802F and is therefor capable to handle larger

projects. And PM803F CPU performance is typically lower around 5% and maximally around 10% than with PM 802F Base Unit.