Rack I/O will be used when using Rack CPUs DCP10 or DCP02. Rack CPUs have no acces to fieldbus based I/O or field devices. Together with AC 800F, Rack I/O may be used when a Rack CPU was replaced by AC 800F or if SoE functionality is necessary. Also the I/O cycles are much faster using Rack I/O than using fieldbus. For example up to 288 binary signals are processed within 2 ms when using only one rack.

The I/O modules link the CPU module and the process for signal matching and signal conversion. They receive data from sensors and contacts, primary detectors, transmitters and other field devices and issue positioning commands and feedback messages to the process.

They have the following tasks and characteristics:

• Input and conversion of conventional types of process signals and signal levels,
• Galvanical isolation between process and system,
• Status LEDs for inputs/outputs,
• Externally-powered outputs,
• Automatic fault detection, fault signaling and temperature monitoring,
• Sensor and line-break monitoring,
• Short-circuit and overload protected digital outputs,
• Digital inputs protected against incorrect polarity
• Isolated analog inputs,
• Replaceable during operation,
• No switches, jumpers or potentiometers, since all settings are configured or configurable with the software,
• Front panel connection of process signals via screw terminals with keyed blocks codeable against incorrect connection.