ABB AC 800M, Manual

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PM891 Processor Unit – General Section 1 Introduction
40 3BSE036351-510 A
PM891 Processor Unit – General
PM891 is a high performance controller, which is capable of handling applications
with high requirements.
PM891 connects to the S800 I/O system through the optical Modulebus. It can act
as a stand-alone Process Controller, or as a controller performing local control tasks
in a control network.
Two PM891 controllers can function together as a redundant pair, with one PM891
acting as the primary controller and the other acting as the backup. The backup
controller takes over the process controller tasks if any hardware error occurs in the
primary controller.
The control network connectivity is obtained by two built in IEEE802.3 Ethernet
channels on PM891.
PM891 also provides a communication expansion bus (CEX-Bus) to which a
number of expansion modules can be connected. These modules offers connectivity
to a wide range of field bus and I/O systems. In case of a redundant pair, both
PM891s are connected to the same CEX-Bus and one of them can control the
modules.
Physically, the PM891 Processor Unit consists of:
• Connector for power supply and status signals (L+, L-, SA, SB).
• DB25 connector for Electrical CEX-Bus.
• External battery connector.
• RJ45 connectors for the two Ethernet channels.
• One Com port.
• Optical Modulebus connector for connection to a maximum of seven clusters,
with 12 non-redundant or six redundant modules (that is, 7x12 = 84 modules).
• Connectors for Redundancy Link.
• SD (Secure Digital) memory connector.
• LEDs.
• Pushbutton reset switch.