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Technical Reference Guide
Compaq Deskpro EXS and Workstation 300 Personal Computers
Featuring the Intel Pentium 4 Processor
First Edition - December 2000
5-5
5.3.1 DISKETTE DRIVE PROGRAMMING
Programming the diskette drive interface consists of configuration, which occurs typically during
POST, and control, which occurs at runtime.
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 47B357 I/O controller during POST.
The configuration registers are accessed through I/O registers 2Eh (index) and 2Fh (data) after the
configuration phase has been activated by writing 55h to I/O port 2Eh. The diskette drive I/F is
initiated by firmware selecting logical device 0 of the 47B357 using the following sequence:
1. Write 07h to I/O register 2Eh.
2. Write 00h to I/O register 2Fh (this selects the diskette drive I/F).
3. Write 30h to I/O register 2Eh.
4. Write 01h to I/O register 2Fh (this activates the interface).
Writing AAh to 2Eh deactivates the configuration phase. The diskette drive I/F configuration
registers are listed in the following table:
Table 5–4. Diskette Drive Controller Configuration Registers
Table 5-4.
Diskette Drive Interface Configuration Registers
Index
Address Function R/W
Reset
Value
30h Activate R/W 01h
60-61h Base Address R/W 03F0h
70h Interrupt Select R/W 06h
74h DMA Channel Select R/W 02h
F0h DD Mode R/W 02h
F1h DD Option R/W 00h
F2h DD Type R/W FFh
F4h DD 0 R/W 00h
F5h DD 1 R/W 00h
For detailed configuration register information refer to the SMSC data sheet for the LPC47B357
I/O component.
5.3.1.2 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 LPC47B357’s I/O-mapped registers listed in
Table 5-5. The diskette drive controller of the LPC47B357 operates in the PC/AT mode in these
systems.
Table 5–5. Diskette Drive Interface Control Registers