Technical Reference Guide
Compaq Deskpro EXS and Workstation 300 Personal Computers
Featuring the Intel Pentium 4 Processor
First Edition - December 2000
4-37
4.8.3 I/O CONTROLLER FUNCTIONS
The I/O controller (used in desktop and minitower systems) contains various functions such as the
keyboard/mouse interfaces, diskette interface, serial interfaces, and parallel interface. While the
control of these interfaces uses standard AT-type I/O addressing (as described in chapter 5) the
configuration of these functions occurs through indexed ports using PnP protocol. In these
systems, hardware strapping selects I/O addresses 02Eh/02Fh at reset as the Index/Data ports for
accessing the logical devices within the I/O contoller. Table 4-16 lists the PnP control registers for
the LPC47B357.
Table 4-16
LPC47B357 Control Registers
Table 4-16.
I/O Controller Control Registers
Index
Function
Reset Value
02h
Configuration Control
00h
03h
Reserved
07h
Logical Device (Interface) Select:
00h = Diskette Drive I/F
01h = Rsvd
02h = Rsvd
03h = Parallel I/F
04h = Serial I/F (UART 1)
05h = Serial I/F (UART 2)
06h = Rsvd
07h = Keyboard I/F
08h = Rsvd
09h = Rsvd
0Ah = Runtime Reg. (GPIO Config.)
0Bh = Rsvd
00h
20h
Super I/O ID Register (SID)
56H
21h
Revision
--
22h
Logical Device Power Control
00h
23h
Logical Device Power Management
00h
24h
PLL / Oscillator Control
04h
25-2Fh
Device specific [2]
--
NOTES:
Refer to LPC47B357 data sheet for detailed register information.
The configuration registers are accessed through I/O registers 2Eh (index) and 2Fh (data) after the
configuration phase has been activated by writing 55h once to I/O port 2Eh. The BIOS then
initiates each logical device and then deactivates the configuration phase by writing AAh to 2Eh.
