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
DRIVE
SELECTED
TAPE SEL1
TAPE SEL2
0
0
1
1
0
1
0
1
None
1
2
3
Table 5 - Internal 4 Drive Decode - Normal
DRIVE SELECT OUTPUTS
(ACTIVE LOW)
MOTOR ON OUTPUTS
(ACTIVE LOW)
DIGITAL OUTPUT REGISTER
Bit 7
X
Bit 6
X
Bit 5
X
Bit 4
1
Bit1
0
Bit 0
0
nDS3
nDS2
nDS1
nDS0 nMTR3 nMTR2 nMTR1 nMTR0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
0
1
1
1
1
nBIT 7
nBIT 7
nBIT 7
nBIT 7
nBIT 7
nBIT 6
nBIT 6
nBIT 6
nBIT 6
nBIT 6
nBIT 5
nBIT 5
nBIT 5
nBIT 5
nBIT 5
nBIT 4
nBIT 4
nBIT 4
nBIT 4
nBIT 4
X
X
1
X
0
1
X
1
X
X
1
0
1
X
X
X
1
1
0
0
0
0
X
X
Table 6 - Internal 4 Drive Decode - Drives 0 and 1 Swapped
DRIVE SELECT OUTPUTS
(ACTIVE LOW)
MOTOR ON OUTPUTS
(ACTIVE LOW)
DIGITAL OUTPUT REGISTER
Bit 7
X
Bit 6
X
Bit 5
X
Bit 4
1
Bit1
0
Bit 0
0
nDS3
nDS2
nDS1
nDS0
nMTR3 nMTR2
nMTR1 nMTR0
1
1
1
0
1
1
1
0
1
1
0
1
1
1
1
1
0
1
1
1
nBIT 7
nBIT 7
nBIT 7
nBIT 7
nBIT 7
nBIT 6
nBIT 6
nBIT 6
nBIT 6
nBIT 6
nBIT 4
nBIT 4
nBIT 4
nBIT 4
nBIT 4
nBIT 5
nBIT 5
nBIT 5
nBIT 5
nBIT 5
X
X
1
X
0
1
X
1
X
X
1
0
1
X
X
X
1
1
0
0
0
0
X
X
24
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