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I/O Systems for Hot Standby CPU Redundancy Systems

Both Series 90-70 Local I/O and Genius I/O systems can be present in a Hot Standby CPU Redundancy control system. The two units are not required to have matching I/O systems. They may have different numbers of I/O racks, and different local I/O or option modules.

Genius I/O System

A Genius I/O system is the I/O system that is included in the redundancy system as shown below. The system can have multiple Genius I/O buses. Any Genius device can be placed on the bus (Genius blocks, Remote I/O Scanner, etc.). The Genius devices are under control of the active unit in the Redundancy system. The Genius Bus Controller in the Primary Unit has a Serial bus Address of 31; the Genius Bus Controller in the Secondary Unit has a Serial Bus Address of 30. Data from Serial Bus Address 31 is the preferred data when data is being sent from both units to devices on the Genius bus.

Local I/O System

Local I/O can be configured in the overall PLC system; however, it is not part of the Hot Standby CPU Redundancy system. Control of Local I/O is done normally through the user's logic program. The user may choose to transfer or not transfer this data. A failure in the Local I/O system will affect the system as described in GFK-0265, the Series 90-70 Programmable Controller Reference Manual.

Cable Connections

The I/O system is configured ºnormallyº except as described below (see the following figure). That is, a Bus Transmitter Module configured in rack 0 is connected through a parallel I/O cable to a Bus Receiver Module in the next rack. The link is continued from this Bus Receiver Module to the Bus Receiver Module in the next rack. This link is continued with a maximum of six expansion racks. Then, the last Bus Receiver is connected via an I/O cable with built-in termination (catalog IC697CBL811 (10 feet (3m)) or IC697CBL826 (25 feet (7.5m)). The last module in the parallel I/O bus link must be a Redundancy Communications Module (RCM). This terminated I/O cable allows replacement of the RCM without interrupting the running system. If no expansion racks are used, the terminated I/O cable is connected directly from the Bus Transmitter Module to the Redundancy Communications Module.

Note

The exception to a normally configured system is that Rack 7, which normally can contain I/O modules is not available for physical I/O modules in a Hot Standby CPU Redundancy system.

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Series 90-70 Hot Standby CPU Redundancy User's Guide ± December 1993

GFK-0827

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State Industries GFK-0827 manual Systems for Hot Standby CPU Redundancy Systems, Genius I/O System, Local I/O System