BASEstar^tm Open DAS
for Allen-Bradley Data Highway^tm
on OpenVMS^tm
Installation and User's Guide

You can connect a PLC to a Local Area Transport (LAT) port. To use a LAT port with the DAS, you must define the LAT port on the OpenVMS system using the LAT control program.

For example, to define port_2 on the LAT node srvr4 as LTA992, enter the following:

$ MCR LATCP LCP> CREATE PORT LTA992 LCP> SET PORT LTA992 /NODE=srvr4/PORT=port_2/NOQUEUE

Use the LAT port name defined above when defining the port to ODS.

You must also set the following SYSGEN parameters to access Allen-Bradley PLCs to reduce the potential for data overruns. Use the SYSGEN utility to display the current values and AUTOGEN to reset the values accordingly. For information on using SYSGEN and AUTOGEN, refer to the OpenVMS System Management Utilities Reference Manual for details.

Parameter	Value
TTY_ALTALARM	0
TTY_ALTYPAHD	1024

To enable use of the alternate typeahead buffer, type the following command from DCL:

$ SET TERM LTA992:/ALTYPEAHD/PERMANENT

For the DAS for Allen-Bradley Data Highway to send and receive data correctly, you must set and define LAT port characteristics to match the line parameters defined in ODS for the corresponding port. The following example shows the characteristics set at the LAT prompt:

Local> DEF PORT n SPEED 9600 Local> DEF PORT n AUTOBAUD DISABLED Local> DEF PORT n AUTOCONNECT DISABLED Local> DEF PORT n FLOW DISABLED Local> DEF PORT n PREFERRED NONE Local> DEF PORT n ACCESS REMOTE Local> DEF PORT n CHAR 8 Local> DEF PORT n PARITY EVEN

2.3.3 Configuring TELNET Access

You can connect a PLC to a terminal server using the TELNET protocol. Using the TELNET protocol allows the use of non-proprietary protocols to access terminal servers to perform device communications.

The terminal server being used must support the BINARY transfer option (RFC 856). The DAS negotiates binary transfer as part of establishing a connection with the port. If the terminal server will not allow binary transfer, the negotiation fails and a connection is not established.

NOTE: Using TELNET communications is slower than either LAT or a directly connected device. Ensure that your throughput requirements will be satisfied before deciding to implement TELNET communications.

For the DAS for Allen-Bradley Data Highway to send and receive data correctly using TELNET, you must set up a port on the terminal server to receive a connect from the DAS. The following example shows setting up a port using a DECserver 700.

Local> DEF TELNET LISTENER y PORT n Local> DEF TELNET LISTENER y CONNECTIONS ENABLED

The following example shows setting up the server for TELNET access. A gateway needs to be configured only if the terminal server is on a different subnet than the host. In general, the terminal server should be on the same subnet as the host in order to reduce communications delays.

Local> DEF INTERNET ADDRESS xx.xx.xx.xx Local> DEF INTERNET MASK xx.xx.xx.xx Local> DEF INTERNET GATEWAY xx.xx.xx.xx

2.3.4 Setting Up Plant-Floor Equipment

To set up your plant-floor equipment, refer to the Allen-Bradley documentation for your specific PLC.

Table 2-5 provides switch settings to use in setting up your KE/KF/KF-2/KF-3 communications card.

Table 2-5 KE / KF / KF-2 / KF-3 Switch Settings

Parameter	Supported	Values
Half Duplex	No
Full Duplex	Yes
Embedded Response	No
BCC Error Check	Yes
CRC Error Check	No
RS-232C Handshaking	Yes 1
Station Number	Yes	1-377 (octal) 2, 1-31 (decimal) 3
Computer Comm Rate	Yes	110 - 19200 4