Compaq 4000N User Manual

Page 101

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Technical Reference Guide

Compaq Deskpro 4000N and 4000S Personal Computers

First Edition - September 1997

5-11

5.3.1

DISKETTE DRIVE PROGRAMMING

5.3.1.1

Diskette Drive Interface Configuration

The diskette drive controller must be configured for a specific address and also must be enabled
before it can be used. Address selection and enabling of the diskette drive interface are affected
by firmware through the PnP configuration registers of the 87307 I/O controller.

The PnP configuration registers are accessed through I/O registers 15Ch (index) and 15Dh
(data). The diskette drive I/F is initiated by firmware selecting logical device 3 of the 87307. This
is accomplished by the following sequence:

1.

Write 07h to I/O register 15Ch.

2.

Write 03h to I/O register 15Dh (this selects the diskette drive I/F).

3.

Write 30h to I/O register 15Ch.

4.

Write 01h to I/O register 15Dh (this activates the interface).

The diskette drive I/F configuration registers are listed in the following table:

Table 5–7. Diskette Drive Controller Configuration Registers

Table 5-6.

Diskette Drive Interface Configuration Registers

Index

Address

Function

R/W

Reset
Value

30h

Activate

R/W

01h

31h

I/O Range Check

R/W

00h

60h

Base Address MSB

R/W

03h

61h

Base Address LSB

R/W

F0h

70h

Interrupt Select

R/W

06h

71h

Interrupt Type

R/W

03h

74h

DMA Channel Select

R/W

02h

75h

Report DMA Assignment

RO

04h

F0h

Configuration Data

R/W

--

F1h

Drive ID

R/W

--

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