Chapter 5 Input/Output Interfaces

 

 

Table 5-5.

 

 

 

Diskette Drive Interface Control Registers

 

Pri.

Sec.

 

 

Addr.

Addr.

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

3F4h

374h

Main Status Register (MSR):

R

 

 

<7> Request for master (host can transfer data) (active high)

 

 

 

<6> Transfer direction (0 – write, 1 = read)

 

 

 

<5> non-DMA execution (active high)

 

 

 

<4> Command busy (active high)

 

 

 

<3,2> Reserved

 

 

 

<1,0> Drive 1, 2 busy (active high)

 

 

 

Data Rate Select Register (DRSR):

W

 

 

<7> Software reset (active high)

 

 

 

<6> Low power mode enable (active high)

 

 

 

<5> Reserved (0)

 

 

 

<4..2> Precompensation select (default = 000)

 

 

 

<1,0> Data rate select (00 = 500 Kb/s, 01 = 300 Kb/s, 10 = 250 Kb/s, 11 = 2/1

 

 

 

Mb/s)

 

3F5h

375h

Data Register:

R/W

 

 

<7..0> Data

 

3F6h

376h

Reserved

--

3F7h

377h

Digital Input Register (DIR):

R

 

 

<7> DSK CHG status (records opposite value of pin)

 

 

 

<6..0> Reserved (0’s)

 

 

 

Configuration Control Register (CCR):

W

 

 

<7..2> Reserved

 

 

 

<1,0> Data rate select (00 = 500 Kb/s, 01 = 300 Kb/s, 10 = 250 Kb/s, 11 = 2/1

 

 

 

Mb/s)

 

NOTE: The most recently written data rate value to either DRSR or CCR will be in effect.

5-6Compaq Deskpro EXS and Workstation 300 Personal Computers

Featuring the Intel Pentium 4 Processor

First Edition – December 2000

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