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FDC37C78-HT

Floppy Disk Controller

Microchip Technology 

TAPE DRIVE REGISTER (TDR)

Address 3F3 READ/WRITE

This register is included for 82077 software

compatability. The robust digital data separator

used in the FDC37C78 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

TAPE SEL1 TAPE SEL2 SELECTED

0

0

None

0

1

1

1

0

2

1

1

3

Table 5 - Internal 4 Drive Decode - Normal

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

1

0 nBIT 7 nBIT 6 nBIT 5 nBIT 4

X

X

1

X

0

1

1

1

0

1 nBIT 7 nBIT 6 nBIT 5 nBIT 4

X

1

X

X

1

0

1

0

1

1 nBIT 7 nBIT 6 nBIT 5 nBIT 4

1

X

X

X

1

1

0

1

1

1 nBIT 7 nBIT 6 nBIT 5 nBIT 4

0

0

0

0

X

X

1

1

1

1 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

13

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