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FDC37M81

PC98/99 Compliant Enhanced Super I/O Controller with Keyboard/Mouse Wake-Up

SMSC -> Microchip 

DIGITAL OUTPUT REGISTER (DOR)

Address 3F2 READ/WRITE

The DOR controls the drive select and motor enables of the disk interface outputs. It also contains the

enable for the DMA logic and a software reset bit. The contents of the DOR are unaffected by a

software reset. The DOR can be written to at any time.

RESET

COND.

7

MOT

EN3

0

6

MOT

EN2

0

5

MOT

EN1

0

4

MOT

EN0

0

3

2

DMAEN nRESE

T

0

0

1

DRIVE

SEL1

0

0

DRIVE

SEL0

0

BIT 0 and 1 DRIVE SELECT

These two bits are binary encoded for the drive

selects, thereby allowing only one drive to be

selected at one time.

BIT 2 nRESET

A logic "0" written to this bit resets the Floppy

disk controller. This reset will remain active

until a logic "1" is written to this bit. This

software reset does not affect the DSR and CCR

registers, nor does it affect the other bits of the

DOR register. The minimum reset duration

required is 100ns, therefore toggling this bit by

consecutive writes to this register is a valid

method of issuing a software reset.

BIT 3 DMAEN

PC/AT and Model 30 Mode:

Writing this bit to logic "1" will enable the DRQ,

nDACK, TC pins and interrupt functions. This

bit being a logic "0" will disable the nDACK, TC

inputs and interrupt functions, and hold the DRQ

output in a high impedance state. This bit is a

logic "0" after a reset and in these modes.

PS/2 Mode: In this mode the DRQ, nDACK, TC

pins and interrupt functions are always enabled.

During a reset, the DRQ, nDACK, TC, and

FINTR pins will remain enabled, but this bit will

be cleared to a logic "0".

BIT 4 MOTOR ENABLE 0

This bit controls the MTR0 disk interface output.

A logic "1" in this bit will cause the output pin to

go active.

BIT 5 MOTOR ENABLE 1

This bit controls the MTR1 disk interface output.

A logic "1" in this bit will cause the output pin to

go active.

BIT 6 MOTOR ENABLE 2

The MTR2 disk interface output is not supported

in the FDC37M81x.

BIT 7 MOTOR ENABLE 3

The MTR3 disk interface output is not supported

in the FDC37M81x.

Table 3 - Drive Activation Values

DRIVE

0

1

DOR VALUE

1CH

2DH

20

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