You can obtain information on controller characteristics by using the Get Device/Volume Information ($GETDVI) system service. (See the HP OpenVMS System Services Reference Manual.)

$GETDVI returns controller characteristics when you specify the item code DVI$_DEVCHAR. Table 9-25 lists these characteristics, which are defined by the $DEVDEF macro and in the file SYS$LIBRARY:DEVDEF.H.

DVI$_DEVTYPE and DVI$_DEVCLASS return the device type and device class names, which are defined by the $DCDEF macro and in the file SYS$LIBRARY:DCDEF.H. The device class name for the LAN Ethernet controllers listed in “Supported LAN Devices” is always DC$_SCOM.

DVI$_DEVBUFSIZ returns the maximum message size. The maximum send or receive message size depends on the packet format and whether padding (NMA$C_PCLI_PAD) is enabled (see “Read” and “Write” ). DVI$_DEVDEPEND returns the unit and line status bits and the error summary bits in a longword field as shown in Figure 9-11.

Figure 9-11 DVI$_DEVDEPEND Returns

Table 9-26 lists the status values and their meanings. These values are defined by the $XMDEF macro. XM$M_STS_ACTIVE is set when the port is started. XM$M_STS_BUFFAIL and XM$M_STS_TIMO are dynamically set and cleared by the LAN driver.

The error summary bits are set when an error occurs. They are read-only bits. If an error is fatal, the Ethernet port is shut down. Table 9-27 lists the error summary bit values and their meanings.