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VT8231
Preliminary Revision 0.8
October 29, 1999
-29-
Register Overview
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R
EGISTERS
Register Overview
The following tables summarize the configuration and I/O
registers of the VT8231. These tables also document the
power-on default value (
“
Default
”
) and access type (
“
Acc
”
)
for each register. Access type definitions used are RW
(Read/Write), RO (Read/Only),
“—”
for reserved / used
(essentially the same as RO), and RWC (or just WC) (Read /
Write 1
’
s to Clear individual bits). Registers indicated as RW
may have some read/only bits that always read back a fixed
value (usually 0 if unused); registers designated as RWC or
WC may have some read-only or read write bits (see
individual register descriptions for details).
Detailed register descriptions are provided in the following
section of this document. All offset and default values are
shown in hexadecimal unless otherwise indicated
Table 2. System I/O Map
Port
00-1F
20-3F
40-5F
60-6F
(60h)
(61h)
(64h)
70-77
78-7F
80
81-8F
90-91
92
93-9F
A0-BF
C0-DF
E0-FF
100-CF7
CF8-CFB
CFC-CFF
D00-FFFF -available for system use-
Function
Master DMA Controller
Master Interrupt Controller 0000 0000 001x xxxn
Timer / Counter
Keyboard Controller
KBC Data
Misc Functions & Spkr Ctrl 0000 0000 0110 xxx1
KBC Command / Status
RTC/CMOS/NMI-Disable 0000 0000 0111 0nnn
-available for system use-
-reserved- (debug port)
DMA Page Registers
-available for system use-
System Control
-available for system use-
Slave Interrupt Controller
Slave DMA Controller
-available for system use-
-available for system use*
PCI Configuration Address 0000 1100 1111 10xx
PCI Configuration Data
Actual Port Decoding
0000 0000 000x nnnn
0000 0000 010x xxnn
0000 0000 0110 xnxn
0000 0000 0110 x0x0
0000 0000 0110 x1x0
0000 0000 0111 1xxx
0000 0000 1000 0000
0000 0000 1000 nnnn
0000 0000 1001 000x
0000 0000 1001 0010
0000 0000 1001 nnnn
0000 0000 101x xxxn
0000 0000 110n nnnx
0000 0000 111x xxxx
0000 1100 1111 11xx
* On-Chip Super-I/O Functions
–
PC-Standard Port Addresses
200-20F
Game Port
2E8-2EF
COM4
2F8-2FF
COM2
378-37F
Parallel Port (Standard & EPP)
3E8-3EF
COM3
3F0-3F1
Configuration Index / Data
3F0-3F7
Floppy Controller
3F8-3FF
COM1
400-402
Parallel Port (ECP Extensions)