Compaq 4000N - Manual (Page 101)

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 --