Watson-Marlow MM420 User Manual
Page 101
Issue 10/06
3 Functions
MICROMASTER 420 Operating Instructions
6SE6400-5AA00-0BP0
101
Baud rate + interval time
Telegram length
Number of nodes (slave)
Master
cycle,master
T
Slave
(MICROMASTER)
cycle,USS
T
cycle,slave(MM4)
T
NOTE
From the user’s perspective, the total cycle time between the master and slave is of significance. As
shown in the diagram above, this time depends on several factors.
Fig. 3-30
Cycle times
Using the USS protocol, a user can establish a serial point-to-point data link and a
serial bus data link between a higher-level master system and several slave
systems. Master systems can be, for example, PLCs (e.g. SIMATIC S7-200) or
PCs. MICROMASTER drive converters are always the slaves on the bus system.
The USS protocol allows the user to implement both automation tasks with cyclical
telegram traffic (
→ a fixed telegram length is necessary) as well as visualization
tasks. In this case, the protocol with variable telegram length is advantageous, as
texts and parameter descriptions can be transferred in one telegram without
chopping up the information.