Input/Output Interfaces

Diskette Drive Interface Control

The BIOS function INT 13 provides basic control of the diskette drive interface. The diskette drive interface can be controlled by software through the SCH5317's I/O-mapped registers listed in Table 5-5. The diskette drive controller of the SCH5317 operates in the PC/AT mode in these systems.

Table 5-5.

Diskette Drive Interface Control Registers

Primary

Second.

 

 

Address

Address

Register

R/W

 

 

 

 

3F0h

370h

Status Register A:

R

 

 

<7> Interrupt pending

 

 

 

<6> Reserved (always 1)

 

 

 

<5> STEP pin status (active high)

 

 

 

<4> TRK 0 status (active high)

 

 

 

<3> HDSEL status (0 = side 0, 1 = side 1)

 

 

 

<2> INDEX status (active high)

 

 

 

<1> WR PRTK status (0 = disk is write protected)

 

 

 

<0> Direction (0 = outward, 1 = inward)

 

 

 

 

 

3F1h

371h

Status Register B:

R

 

 

<7,6> Reserved (always 1’s)

 

 

 

<5> DOR bit 0 status

 

 

 

<4> Write data toggle

 

 

 

<3> Read data toggle

 

 

 

<2> WGATE status (active high)

 

 

 

<1,0> MTR 2, 1 ON- status (active high)

 

 

 

 

 

3F2h

372h

Digital Output Register (DOR):

R/W

 

 

<7,6> Reserved

 

 

 

<5,4> Motor 1, 0 enable (active high)

 

 

 

<3> DMA enable (active high)

 

 

 

<2> Reset (active low)

 

 

 

<1,0> Drive select (00 = Drive 1, 01 = Drive 2, 10 = Reserved, 11 =

 

 

 

Tape drive)

 

 

 

 

 

3F3h

373h

Tape Drive Register (available for compatibility)

R/W

 

 

 

 

 

5-6

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Technical Reference Guide