TAPE DRIVE REGISTER (TDR)
Address 3F3 READ/WRITE
This register is included for 82077 software compatability.
The robust digital data separator used in the
FDC37C669 does not require its characteristics modified
for tape support. The contents of this register are not
used internal to the device. The TDR is unaffected by a
software reset. Bits 2-7 are tri-stated when read in this
mode.
Table 4- Tape Select Bits
TAPE SEL1
0
0
1
1
TAPE SEL2
0
1
0
1
DRIVE
SELECTED
None
1
2
3
Table 5 - Internal 4 Drive Decode - Normal
DIGITAL OUTPUT REGISTER
DRIVE SELECT OUTPUTS
(ACTIVE LOW)
Bit 7 Bit 6 Bit 5 Bit 4 Bit1 Bit 0 nDS3 nDS2 nDS1 nDS0
X
X
X
1
0
0
1
1
1
0
X
X
1
X
0
1
1
1
0
1
X
1
X
X
1
0
1
0
1
1
1
X
X
X
1
1
0
1
1
1
0
0
0
0
X
X
1
1
1
1
MOTOR ON OUTPUTS
(ACTIVE LOW)
nMTR3 nMTR2 nMTR1 nMTR0
nBIT 7 nBIT 6 nBIT 5 nBIT 4
nBIT 7 nBIT 6 nBIT 5 nBIT 4
nBIT 7 nBIT 6 nBIT 5 nBIT 4
nBIT 7 nBIT 6 nBIT 5 nBIT 4
nBIT 7 nBIT 6 nBIT 5 nBIT 4
Table 6 - Internal 4 Drive Decode - Drives 0 and 1 Swapped
DIGITAL OUTPUT REGISTER
DRIVE SELECT OUTPUTS
(ACTIVE LOW)
MOTOR ON OUTPUTS
(ACTIVE LOW)
Bit 7 Bit 6 Bit 5 Bit 4 Bit1 Bit 0 nDS3 nDS2 nDS1 nDS0 nMTR3 nMTR2 nMTR1 nMTR0
X
X
X
1
0
0
1
1
0
1
nBIT 7 nBIT 6 nBIT 4 nBIT 5
X
X
1
X
0
1
1
1
1
0
nBIT 7 nBIT 6 nBIT 4 nBIT 5
X
1
X
X
1
0
1
0
1
1
nBIT 7 nBIT 6 nBIT 4 nBIT 5
1
X
X
X
1
1
0
1
1
1
nBIT 7 nBIT 6 nBIT 4 nBIT 5
0
0
0
0
X
X
1
1
1
1
nBIT 7 nBIT 6 nBIT 4 nBIT 5
24