Rockwell Automation Publication 2080-UM002N-EN-E - November 2022 343
Appendix G Connect to Networks using DF1
Having determined the maximum message transmission time (224 ms), the average slave
program scan time (20 ms) and the largest of either RTS Send Delay (60 ms) or the modem
turnaround time, the minimum ACK timeout is simply the sum of these values.
DF1 Half-Duplex Master Communication Diagnostics
Communication diagnostics is available while connected to the controller by clicking the
Diagnose communication status button. Table 94 explains information regarding the
diagnostic counter data displayed.
Configure a Message-based
Mode DF1 Half-Duplex
Master Station
Choose message-based communication mode if you want to use MSG instructions in user
programming to communicate with one station at a time. If your application uses satellite
transmission or cellular transmission, consider choosing message-based. Communication to a
slave station can be initiated on an as-needed basis.
With message-based mode, you do not have an active node file that you can use to monitor
station status. Also, you cannot implement slave station-to-slave station messaging or slave
programming.
Parameter Example Values (in ms)
Max Message Transmission Time 224
Average Program Scan Time 20
RTS Send Delay 60
Modem Turnaround Time 50
Calculated ACK Timeout 304
Round up to Nearest 20 ms 320
Table 94 - DF1 Half-Duplex Master Communication Diagnostics Parameters
Status Field Definition
Packets Sent
The total number of DF1 messages sent by the controller (including message
retries).
Packets Received The number of messages received with no errors.
Last Normal Scan Time (ms) Time in millisecond increments of last scan through Normal Poll List.
Last Priority Scan Time (ms) Time in millisecond increments of last scan through Priority Poll List.
Message Retried The number of message retries sent by the controller.
Undelivered Packets
The number of messages that were sent by the controller but not acknowledged by
the destination device.
Duplicate Received
The number of times the controller received a message packet identical to the
previous message packet.
Bad Packet Received
The number of incorrect data packets received by the controller for which no ACK
was returned.
Max Normal Scan Time (ms) Maximum time in millisecond increments to scan the Normal Poll List.
Max Priority Scan Time (ms) Maximum time in millisecond increments to scan the Priority Poll List.
Use only the largest of these two values.
1. Click Diagnose communication status to bring
up the DF1 Half-Duplex Master diagnostics.
2. See Table 94 for details concerning the DF1
Half-Duplex Master Communication
Diagnostics screen.
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