Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 237)

Publication AG-UM008C-EN-P - February 2005
Configuring Logix Controllers 7-11
Minimum DF1 Half-Duplex Master ACK Timeout
The governing timeout parameter to configure for a DF1 Half-Duplex
Master is the ACK Timeout. The ACK Timeout is the amount of time
you want the controller to wait for an acknowledgment of its message
transmissions. Set in 20 millisecond intervals, the value is the amount
of time the master will wait for:
•
an ACK to be returned by a slave when the master has just sent
it a message, or
•
a poll response or message to be returned by a slave when the
master has just sent it a poll packet.
The timeout must be long enough that after the master has transmitted
the last character of the poll packet, there is enough time for a slave to
transmit (and the master receive) a maximum sized packet before the
time expires.
To calculate the minimum ACK timeout, you must know:
•
the modem baud rate
•
maximum sized data packet (the maximum number of data
words that a slave write command or read reply packet might
contain)
•
the RTS/CTS or turnaround delay of the slave modem
•
the configured RTS Send Delay in the slave
•
the program scan time of the slave