Lantronix XPress-DR UDS1100-IAP - Multi-Master DF1 Protocol User Guide - Page 6

2: Applications RSLinx, HMI, or OPC The most common use of the Multi-Master DF1 firmware is to allow two remote masters (for example, two HMI/OPC servers or one HMI and one RSLogix) to talk to the PLC at the same time. Figure 2-1. Computer to PLC The Multi-Master DF1 firmware understands the DF1 protocol enough to prevent conflict between the masters. For example, it prevents two remote copies of RSLogix from locking the PLC resources. The first will be granted the resource, and the second will be rejected as the resource is locked already. PLC to PLC Communication (MSG blocks) Another use is to allow the attached PLC to issue MSG blocks for peer-to-peer communications. While the picture at right just shows three PLCs, you could also have HMI masters and others attached to some or all of the PLCs. Figure 2. - PLC to PLC The Multi-Master DF1 firmware allows four incoming and one outgoing socket to be active at one time. This means in a simple example, that IAP Device Server-C with Multi-Master DF1 firmware can allow sockets from IAP Device Server-A, IAP Device Multi-Master DF1 Protocol User Guide 5