Installation manual

Publication 1747-RM001G-EN-P - November 2008
13-72 SLC Communication Channels
Error
Detection
CRC With this selection, you choose the how the processor checks the accuracy of each DF1 packet
transmission.
BCC: This algorithm provides a medium level of data security. It cannot detect:
• transposition of bytes during transmission of a packet.
• the insertion or deletion of data values of zero within a packet.
CRC: This algorithm provides a higher level of data security.
Select an error detection method that all devices in your configuration can use.
When possible, choose CRC.
Duplicate
Packet
Detect
Checked Duplicate Detect lets the SLC detect if it has received a message that is a duplicate of its most
recent message from the master station. If you choose duplicate detect, the processor will
acknowledge (ACK) the message but will not act on it since it has already performed the
message’s task when it received the command from the first message.
If you want to detect duplicate packets and discard them, leave this parameter checked. If you
want to accept duplicate packets and execute them, uncheck this parameter.
Poll Timeout 3000 The timer keeps track of how often in 20 ms increments that the station is polled. If the station
has a message to send, it starts the timer.
If the poll timeout expires before the message timeout, which you specify in the MSG control
block, the MSG error bit is set and the message is removed from the transmit queue.
If the message timeout, which you specify in the MSG control block, expires before the poll
timeout expires, the MSG error bit and MSG timeout bit are set. You should always make the
MSG timeout greater than the poll timeout so this does not happen.
The poll timeout can be disabled by entering a zero. See page page 13-73 for recommendations
to minimize this value
RTS Off
Delay
0 Defines the amount of time in 20 millisecond increments that elapses between the end of the
message transmission and the de-assertion of the RTS signal. This time delay is a buffer to
make sure that the modem has transmitted the message, but should normally be left at zero. See
page 13-89 for further guidelines for setting this parameter.
RTS Send
Delay
0 Defines the amount of time in 20 millisecond increments that elapses between the assertion of
the RTS signal and the beginning of the message transmission. This time allows the modem to
prepare to transmit the message. The Clear-to-Send (CTS) signal must be high for transmission
to occur.See page 13-89 for further guidelines for setting this parameter.
Table 13.22 Define these parameters when configuring a SLC 5/03, 5/04, or 5/05 processor as a slave station. (Continued)
Tab Parameter Default Selections