Input/Output Interfaces

Table 5-8. (Continued)

Diskette Drive Interface Control Registers

Primary

Second.

 

 

Address

Address

Register

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.

5-10

361834-002

Technical Reference Guide