ABBAC 800M Controller Hardware

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.

shows the front view, Figure 9 shows the top view, and Figure 10 shows the 

bottom view of PM891.

Screw terminals are provided for connections to the power supply and the external 

battery. 

The 24 V DC power supply powers all the units on the CEX-Bus. The optical 

module clusters are powered independently.

PM891/PM86x/TP830 Processor Unit – Redundancy

Processor unit redundancy is available for PM861, PM864, PM865, PM866, and 

PM891. In this case, the controller contains two processor units, each including 

memory for system and application software. One unit is acting as primary, the 

other is backup (hot stand-by). The primary processor unit controls the process. The 

backup stands by, ready to take over in case of a fault in the primary. The 

changeover is done bumplessly and in less than 10 ms. During the changeover, the 

process outputs are frozen.

Following a changeover, the system operates as a system without redundancy with 

only one processor unit in operation. You can replace the malfunctioning processor 

unit while the system is running. After the replacement is carried out, the system 

once again has a redundant processor unit.

If an error arises in the backup unit, you can also replace the backup unit while the 

system is running.

Errors which occur in the backup unit can never affect the primary unit's operation. 

The primary unit and the backup unit are logically separated from one another. 

Hardware errors in the primary processor unit cause the system to perform a correct 

changeover. These hardware errors are single errors.

The application programming and the communication are totally unaffected by the 

redundancy.

PM86x/TP830 Redundancy

The PM861/PM864/PM865/PM866 has an RCU Link Connector for connecting the 

RCU Link Cable (see Figure 2 on page 32). In a redundant system the two processor 

units are linked together with the RCU Link Cable (max 1 m). Both processor units 

are also connected to the same CEX-Bus and either of the two can control the 

expansion units (see Figure 29 on page 93).

S800 I/O units are connected to the two CPUs via the optical ModuleBus and two 

TB840 cluster modems on each S800 I/O cluster (see Figure 55 on page 161). The 

built-in electrical ModuleBus on the TP830 baseplate cannot be used for connecting 

S800 I/O in a redundant system.

The serial port, COM3 on the baseplate TP830, cannot be used in redundant CPU 

configuration.