The maximum support for a single-level remote module extension depends on the specific system, but for Rockwell Automation MRB01XS/MRB04XM modules, a single remote chassis can support up to three slave modules per master module.

Rockwell Automation Remote Bus Extender

For the MRB01XS Remote Bus Extender Slave Module, each remote chassis can accommodate three slave modules in the designated slots (A, B, and C). These slave modules connect via fibre optic cables to a corresponding MRB04XM master module in the local chassis, which interfaces with the processor modules (MPPs) in the main chassis . This configuration represents a single-level remote extension, meaning all slave modules are directly connected to a single master without additional tiers. The system is designed to maintain reliable communication and I/O integration within this limit.

Key Considerations

• Chassis Slots: Only three slots are available for slave modules in a single remote chassis.
• Communication: Fibre optic links ensure high-speed, low-latency communication between master and slave modules.
• Environmental Limits: Maximum ambient temperature at the hottest point should not exceed 60°C .
• Physical Constraints: The MRB01XS is a 9U high PCB with an integral front panel, so physical space in the chassis is a limiting factor.

Siemens S7-1200 Expansion Analogy

For Siemens S7-1200 CPUs, single-level expansion is achieved using signal modules (SMs), communication boards (CBs), and other plug-in modules. Each SM connects directly to the CPU, providing additional I/O or communication capabilities . While the exact number of modules depends on the CPU model and available slots, the principle is similar: a single-level extension is limited by the number of physical connections and supported communication channels.

Summary

• Rockwell MRB01XS/MRB04XM: Maximum of three slave modules per master in a single remote chassis.
• Siemens S7-1200: Limited by CPU slots and module type; single-level expansion is constrained by physical and communication capacity.
• General Rule: Single-level remote module extensions are constrained by available slots, communication bandwidth, and environmental specifications. Multi-level or cascading extensions require additional master modules or hierarchical configurations. This information helps in planning remote I/O expansions while ensuring system reliability and compliance with manufacturer specifications.