Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 81)

Publication AG-UM008C-EN-P - February 2005
Configuring MicroLogix 1100/1200/1500 Controllers 3-13
Table 3.1 MicroLogix 1100/1200/1500 Master Using Standard-Communication Mode
Parameter Selections
Baud Rate Select a communication rate that all devices in your system support. Configure all
devices in the system for the same communication rate.
Parity Parity provides additional message packet error detection. To implement even
parity checking, choose Even. To implement no parity checking, choose None.
Node Address A node address identifies the controller on the DF1 half-duplex link. Each station
on a link must have a unique address. Choose an address between 0
10
and 254
10.
Node address 255
10
is the broadcast address, and cannot be selected as a
station’s individual address.
Control Line This parameter defines the mode in which the driver operates. Choose a method
appropriate for your system’s configuration:
•
If you are not using a modem, choose NO HANDSHAKING.
•
If the master modem is full duplex, choose FULL-DUPLEX MODEM (RTS
ON).
•
If all the modems in the system are half-duplex, choose HALF-DUPLEX
MODEM (RTS/CTS Handshaking).
See page 3-8 for a description of the control line operation settings.
Error Detection With this selection, you choose how the controller 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.
Polling Mode If you want to receive:
•
only one message from a slave station per its turn, choose STANDARD
(SINGLE MESSAGE TRANSFER PER NODE SCAN). Choose this method only
if it is critical to keep the poll list scan time to a minimum.
•
as many messages from a slave station as it has, choose STANDARD
(MULTIPLE MESSAGE TRANSFER PER NODE SCAN).
Duplicate Packet Detect Duplicate Detect lets the controller detect if it has received a message that is a
duplicate of its most recent message from another 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, check this parameter. If
you want to accept duplicate packets and execute them, leave this parameter
unchecked.
ACK Timeout The amount of time, in 20 millisecond increments, that you want the controller to
wait for an acknowledgment to the message it has sent before the processor
retries the message or the message errors out. This timeout value is also used for
the poll response timeout. See page 3-14 for recommendations to minimize this
value.
RTS Off Delay 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 3-11 for further guidelines for setting
this parameter.