Digi 90000566_H manual Priority=highmediumlow, Medium

set ia

priority={highmediumlow}

Normally messages are processed in a fair round-robin scheme. This becomes unfair when one master acts as many – for example opening 16 TCP sockets to talk to 16 slaves contrasted to a second master using a single TCP socket to talk to 16 slaves. In this situation, the device assumes it has 17 masters and in effect the first master will have 16 requests answered for every one the second master succeeds in getting answered. This option can be used to adjust the handling of serial master requests. For example, set the serial master to High and the network masters to medium. The effectiveness of this option depends on the protocol behavior – so while some Modbus systems will find it useful, it has no effect on most Rockwell protocols.

high

A high-priority master can get up to 50 percent of the bandwidth – of course you cannot have too many high-priority masters. All high- priority masters with queued messages get one message serviced before any low or medium priority masters get any service.

medium

If a high-priority master has queued messages, then one medium- priority master gets one message serviced before all the high- priority masters are offered service again. If only medium-priority masters exist (which is the default setting), then all masters are serviced in a round-robin manner.

low

Low-priority masters only get service when no High- or Medium- priority master has messages to service.

The default is “medium.”

Chapter 2 Command Descriptions 123