Specifications

Data Structures
1.10 Driver Prologue Table (DPT)
Table 1–12 (Cont.) Contents of Driver Prologue Table
Field Name Contents
DPT$V_TPALLOC Select the tape allocation class parameter.
DPT$V_SNAPSHOT Driver is certified for system snapshot.
DPT$V_NO_IDB_DISPATCH Do not select IDB$L_UCBLST for UCB
vectors.
DPT$V_EXTENDED_DDT Do not allocate an extended DDT.
DPT$V_XPAMOD Driver is compliant with extended
addressing (XA).
DPT$V_VERSION_SAFE Driver is exempt from version checks.
DPT$W_INITTAB Offset to driver initialization table. Every driver must specify a list of data
structure fields and values to be written into the fields at the time that the
driver-loading procedure creates the driver’s data structures and loads the
driver.
The driver invokes the system macro DPT_STORE to specify these fields
and their values.
DPT$W_REINITTAB Offset to driver-reinitialization table. Every driver must specify a list of
data structure fields and values to be written into these fields at the time
that the driver-loading procedure creates the driver’s data structures and
loads the driver or the driver is reloaded.
The driver invokes the system macro DPT_STORE to specify these fields
and their values.
DPT$W_UNLOAD Relative address of driver routine to be called when driver is reloaded. The
driver specifies this field with the value of the unload argument to the
DPTAB macro. The driver-loading procedure calls the driver unloading
routine before reinitializing all device units associated with the driver.
DPT$W_MAXUNITS Maximum number of units on controller that this driver supports. Specify
this value in the maxunits argument to the DPTAB macro. If no value is
specified, the default is eight units.
DPT$W_VERSION* Version number that identifies format of DPT. The DPTAB macro
automatically inserts a value in this field. SYSGEN checks its copy of
the version number against the value stored in this field. If the values
do not match, an error is generated. To correct the error, reassemble and
relink the driver.
DPT$W_DEFUNITS Number of UCBs that the autoconfiguration facility will automatically
create. Drivers specify this number with the defunits argument to the
DPTAB macro. If the driver also gives a value to DPT$W_DELIVER, this
field is also the number of times that the autoconfiguration facility calls
the unit delivery routine.
DPT$W_DELIVER Relative address of the unit delivery routine that the autoconfiguration
facility calls for the number of UCBs specified in DPT$W_DEFUNITS.
The driver supplies the address of the unit delivery routine in the deliver
argument to the DPTAB macro.
DPT$W_VECTOR Relative address of a driver-specific vector. A terminal class or port driver
stores the address of its class or port entry vector table in this field.
DPT$T_NAME Name of the device driver. Field is 12 bytes. One byte records the length
of the name string; the name string can be up to 11 characters. Drivers
specify this field as the value of the name argument to the DPTAB macro.
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