User manual

Publication AG-UM008C-EN-P - February 2005
1-10 Designing Communication
Figure 1.3 How a Master Station Requests Data
To design a communication scheme using standard-communication
mode, you must do the following:
• design a polling scheme
• plan for timing issues
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• Ladder logic
triggers MSG
• Master driver
formats command
packet
Master data table
ACK timeout received and
tries > ‘DF1 message
retries’ return error
indication
• Send command
packet
• Start ACK timer
• Wait for ACK (or
timeout)
• Start reply timer
• Resume polling
• Wait for reply (or
timeout)
reply packet
received return
data
reply timeout received
return error
indication
ACK received
ACK timeout received
and station active and
tries < or = ‘DF1 message
retries’