Product specifications

Data Exchange Protocol Without Acknowledge
322 3BDS011222-510 B
Figure 194 shows the detailed view of protocol work flow.
Characteristics of the protocol is listed below:
• A protocol cycle is always initiated by the PLC. It will prepare data and raise
Command bit when the state is 0.
• PLC will lower its Command bit by itself. The data will be lost, if the PC has
not read the data at that time.
• PLC can TRIGGER PC with the same Command bit status at some specified
interval. (i.e. It may increment Retry Counter and write the changed TRIGGER
word to the PC repeatedly).
• This protocol is also prepared with a simple transaction control feature.
Transaction Counter occupies 2 most significant bytes of the TRIGGER word.
If PLC increments Transaction Counter between protocol cycles (with
Figure 194. Data Exchange Protocol without Acknowledge, detailed description