Introduction

Determinism refers to the ability to calculate and predict application response time (ART), which is the time required for an M580 network system to detect and respond to a single input. When you calculate ART for your application, consider the following:

• An M580 architecture features a dedicated module for RIO communications.

• Each remote packet travels from an input module in the remote drop to the controller, then back to an output module in the remote drop.

• Hop count is defined as the number of switches (including switches embedded in RIO devices) that a packet passes through to reach its destination.

• Packet path impacts jitter calculations, because of potential queue delays along its path.

• For RIO ART calculations:

  • Consider the worst case, i.e., the longest path a packet may need to travel in case of a broken network cable.

  • RIO only provides recovery from a single break in the system. This remains true even if a packet is able to arrive at its destination when multiple breaks exist in the system.

  • Only count hops and jitter delays along the network path, i.e., from the perspective of the specific RIO adapter module transmitting the packet. Do not include hops and jitter for other devices in the system that are not on the network path.