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The ILAN$MAX_SPT_REQUESTS parameter specifies the total number of blocks that can be allocated in the SPT (support) global section. DASes use blocks in the global section for storing data structures and for doing device I/O. The SPT global section is sized by calculating the number of SMALL, MEDIUM, LARGE and EXTRA LARGE blocks that the section should contain. Some blocks remain for the life of a device and some are allocated and deallocated for each I/O operation. Table 2-8 shows the static blocks of each size that are used by the DAS.
| PE/NI | Block Size | Quantity1 | Block Type |
|---|---|---|---|
| PE | MEDIUM | 1 | Device |
| 7 2 | Device 3 | ||
| SMALL | 1 | Device 3 | |
| Modbus NI | MEDIUM 4 | 1 | Line |
| SMALL | 1 | Device | |
| 1 | DAS | ||
| Modbus-Plus NI | LARGE | 2 5 | Device |
| MEDIUM | 1 | Line | |
| SMALL | 1 | Device | |
| 7 2 | Device 3 | ||
| 1 | DAS | ||
| TCP/IP NI | LARGE | 1 | Device |
| MEDIUM | 1 | DAS | |
| 7 2 | Device |
Table 2-9 shows the dynamic blocks of each size that are used by the DAS. These blocks are created and deleted as the device does I/O. I/O can be initiated solicitedly by a user or a polling set or can be initiated unsolicitedly by the device.
| PE/NI | Block Size | Quantity1 | I/O Type |
|---|---|---|---|
| PE | MEDIUM | 1 | Any |
| Modbus NI | MEDIUM 2 | 1 | Any |
| Modbus-Plus NI | LARGE | 1 | Any |
| TCP/IP NI | MEDIUM | 1 | Any |
The size of the SPT global section can be tuned by changing the
percentage of each kind of block that is created. Refer to the
BASEstar Classic Configuration and Tuning Guide for instructions on changing the percentage of each size
of block that is created in the global section.
2.3.3 Configuring Ports
A device can be physically connected to a local area transport (LAT) port. To use a LAT port with the DAS, you must define the LAT port on the host system by using the LAT control program. The following DCL example shows how to define port_2 on the LAT node srvr4 as LTA992. It is very important when defining the LAT port to use the /NOQUEUE option. If the port is owned by another process device connection management reports an error during the establishment of a connection to the device. When you define a path and a device to BASEstar Classic device connection management LTA992 is supplied as the VAXport.
$ MCR LATCP LCP> CREATE PORT LTA992 LCP> SET PORT LTA992 /NODE=srvr4/PORT=port_2/NOQUEUE |
For the DAS to send and receive data correctly, you must set and define LAT port characteristics to match the line parameters of the path definition for devices and terminals connected to the LAT. An example of the characteristics set at the LAT prompt follows:
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 |
You must also set the following SYSGEN parameters to access Modicon programmable controllers 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 |
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