ZiLOG Z80-RIO Operating System User's Manual page 32

of the supplemental parameter vector with bits 7 and 1
reset to (this file name string must be terminated by a
delimiter). RIO then moves the file name into the file
name field of the supplemental parameter vector and sets
the name length and drive designation. If no name is
given, the name length field is set to zero. If no drive
designation is given, the standard search sequence symbol
'*'
is put in the drive designation field. More
importantly, the logical unit referenced in the request
vector is linked to the device specified as part of the
file name string, or the master device, if no device name
is given.
As a second alternative, the user program can set bit 1 of
the flag byte after moving (or assembling) the entire
parameter string into the supplemental parameter vector
file name field. RIO then formats the rest of the
supplemental parameter vector in the same
wa~
as before.
If bit 7 of the flag byte is set (=1), the vector (and
supplemental parameter vector) is assumed to be in a
correct format, i.e., all fields hold valid information.
If bit
0
is also set, the unit is linked to the master
device. If bit 0 is reset, unit redefinition does not
occur, maintaining the current unit-device link. In this
last case, previous unit definition must have taken place.
After the preceding steps are taken, the I/O request is
passed to the intended device for processing. Subsequent
I/O requests are routed directly to the device.
The following table summarizes the effects of specific
supplemental parameter vector flag byte values during the
'ASSIGN' I/O request:
Flag Byte
(hex)
o
(bit 1 reset)
2 (bit 1 set)
Effect on ASSIGN I/O Request
RIO formats Supplemental
Parameter Vector, Data Transfer
Address is the address of the
file name string
RIO formats Supplemental
Parameter Vector, file name
field contains file name
string
- 20 -