The GE-Emerson IC695CRU320 PACSystems Rx3i Redundancy CPU communicates with the programmer and HMI devices via a serial port using SNP Slave protocol. It communicates with I/O and smart option modules over a dual backplane bus that provides a high-speed PCI backplane for fast throughput of new advanced I/O, as well as a serial backplane for easy migration of existing Series 90-30 I/O.
The CPU provides Hot standby (HSB) redundancy. Two redundant units make up a redundancy system. Each unit requires one Redundancy CPU (CRU320 and a redundancy Memory Xchange module (IC695RMX128/228) configured as a redundancy link.
The CPU's components are considered open equipment (having live electrical parts that may be accessible to users) and must be installed in an ultimate enclosure that is manufactured to provide safety. At a minimum, the enclosure shall provide a degree of protection against solid objects as small as 12mm. This equates to a NEMA/UL Type 1 enclosure or an IEC60529 IP20 rating, providing at least a pollution degree 2 environment.