Specifications

Data Structures
1.7 Channel Request Block (CRB)
Table 1–9 (Cont.) Contents of Interrupt Transfer Vector Block (VEC)
Field Name Contents
VEC$B_DATAPATH Data path specifier. The bits that make up this field are used as follows:
VEC$V_DATAPATH Number of data path used in DMA transfer. The
routine IOC$REQDATAP writes this 5-bit field
when a buffered data path is allocated and clears
the field when the data path is released.
The routine IOC$LOADUBAMAP copies the
contents of this field into UNIBUS adapter map
registers. These bits also serve as implicit input
to the IOC$PURGDATAP routine.
VEC$V_LWAE Longword access enable (LWAE) bit. Drivers set
this bit when they wish to limit the data path
to longword-aligned, random-access mode. The
routine IOC$LOADUBAMAP copies the value in
this field to the UNIBUS adapter map registers.
<6> Reserved to Digital.
VEC$V_PATHLOCK Buffered data path allocation indicator. Drivers
set this bit to specify that the buffered data path
is permanently allocated.
VEC$L_ADP* Address of ADP. The SYSGEN command CONNECT must specify the nexus
number of the UNIBUS adapter used by a controller. The driver-loading
procedure writes the address of the ADP for the specified UBA into the
VEC$L_ADP field.
IOC$REQMAPREG, IOC$REQALTMAP, and IOC$RELMAPREG read and
write fields in the ADP to allocate and deallocate map registers.
VEC$L_UNITINIT* Address of device driver’s unit initialization routine. If a device unit requires
initialization at driver-loading time and during recovery from a power
failure, the driver specifies a value for this field in the DPT. The driver-
loading procedure calls this routine for each device unit each time the
procedure loads the driver. The power failure recovery procedure also calls
this routine to initialize device units after a power failure.
MASSBUS drivers that support mixed device types must not use this
field. Instead, they should specify the unit initialization routine in the
unit initialization field of the DDT (DDT$L_UNITINIT). Other drivers can
use either field.
VEC$L_START* Address of system start protocol routine. Use of this field is reserved to
Digital.
VEC$L_UNITDISC* Address of unit disconnect routine. Use of this field is reserved to Digital.
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