58
Rockwell Automation Publication 5069-UM003B-EN-P - January 2020
Chapter 3
Compact 5000 I/O Serial Module Features
Use the following table to understand the communication parameters needed to
configure a serial module as a master station using message-based communication
mode parameter.
Field
Description
Default
Station Address
The station address for the serial port on the DF1 master. Enter a valid DF1 address (0…254).
0
Transmit Retries
Specifies the number of times a message is retried after the first attempt before being declared undeliverable. Enter a value
0…127.
3
ACK Timeout
Specifies the amount of time you want the controller to wait for an acknowledgment to its message transmission. Enter a
value 0…32767. Limits are defined in 20 ms intervals.
50(1000 ms)
Polling Mode
If you want to:
• Accept unsolicited messages from slave stations, choose MESSAGE BASED (Allow slave to initiate messages.) Slave station-
initiated messages are acknowledged and processed after all master station-initiated (solicited) messages.
Note: Slave stations can only send messages when they are polled. If the message-based master station never sends a slave
station a message, the master station will never send the slave station a poll. Therefore, to regularly obtain a slave station-
initiated message from a slave station, you should choose to use standard communications mode instead.
• Ignore unsolicited messages from slave stations, choose MESSAGE BASED (Do not allow the slave to initiate messages.)
Slave station-initiated messages are acknowledged and discarded. The master station acknowledges the slave station-
initiated message so that the slave station removes the message from its transmit queue, which allows the next packet
that is slated for transmission into the transmit queue.
Message-Based (slave can
initiate messages)
Error Detection
Select BCC or CRC error detection.
Configure all stations to use the same type of error checking.
BCC—
The serial module sends and accepts messages that end with a BCC byte for error checking. BCC is quicker and easier to
implement, but does not detect as many errors as CRC
CRC—
the serial module sends and accepts messages with a 2-byte CRC for error checking. CRC is a more effective error
detection algorithm.
BCC
Enable Duplicate
Detection
Select whether the serial module should detect and ignore duplicate messages.
Enabled