Installation manual

Publication 1747-RM001G-EN-P - November 2008
SLC Communication Channels 13-61
Minimum DF1 Half-duplex Master Channel 0 ACK Timeout
The governing timeout parameter to configure for a DF1 Half-duplex Master
is the channel 0 ACK Timeout. The ACK Timeout is the amount of time you
want the processor 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.