TAPE DRIVE REGISTER (TDR)
Address 3F3 READ/WRITE
TABLE 7 - TAPE SELECT BITS
TAPE SEL1
TAPE SEL0
(TDR.0)
DRIVE
SELECTED
(TDR.1)
0
0
1
1
0
1
0
1
None
1
2
3
The Tape Drive Register (TDR) is included for
82077 software compatibility and allows the user
to assign tape support to a particular drive during
initialization. Any future references to that drive
automatically invokes tape support. The TDR
Tape Select bits TDR.[1:0] determine the tape
drive number. TABLE 7 illustrates the Tape Select
Bit encoding. Note that drive 0 is the boot device
and cannot be assigned tape support. The
remaining Tape Drive Register bits TDR.[7:2] are
tristated when read. The TDR is unaffected by a
software reset.
22
SMSC [ SMSC CORPORATION ]
