VT82C686B
Offset 81 – ISA Positive Decoding Control 1 ..................RW
Offset 83 – ISA Positive Decoding Control 3.................. RW
7
On-Board I/O Port Positive Decoding
7
COM Port B Positive Decoding
0
Disable ...................................................default
0
Disable................................................... default
1
Enable
1
Enable
6
Microsoft-Sound System I/O Port Positive
Decoding
6-4 COM-Port B Decode Range
000 3F8h-3FFh (COM1)............................ default
001 2F8h-2FFh (COM2)
010 220h-227h
0
Disable ...................................................default
1
Enable
011 228h-22Fh
100 238h-23Fh
101 2E8h-2EFh (COM4)
110 338h-33Fh
5-4 Microsoft-Sound System I/O Decode Range
00 0530h-0537h ..........................................default
01 0604h-060Bh
10 0E80-0E87h
11 0F40h-0F47h
111 3E8h-3EFh (COM3)
3
2
APIC Positive Decoding
3
COM Port A Positive Decoding
0
Disable ...................................................default
0
Disable................................................... default
1
Enable
1
Enable
BIOS ROM Positive Decoding
2-0 COM-Port A Decode Range
000 3F8h-3FFh (COM1)............................ default
001 2F8h-2FFh (COM2)
010 220h-227h
0
Disable ...................................................default
1
Enable
........................................ always reads 0
1
0
Reserved
011 228h-22Fh
PCS0 Positive Decoding
0
Disable ...................................................default
100 238h-23Fh
1
Enable
101 2E8h-2EFh (COM4)
110 338h-33Fh
111 3E8h-3EFh (COM3)
Offset 82 – ISA Positive Decoding Control 2 ..................RW
7
FDC Positive Decoding
Offset 84 – ISA Positive Decoding Control 4.................. RW
0
Disable ...................................................default
1
Enable
........................................always reads 0
7-4 Reserved
6
LPT Positive Decoding
3
FDC Decoding Range
0
Disable ...................................................default
0
Primary .................................................. default
1
Enable
1
Secondary
5-4 LPT Decode Range
00 3BCh-3BFh, 7BCh-7BEh.......................default
2
Sound Blaster Positive Decoding
0
Disable................................................... default
01 378h-37Fh, 778h-77Ah
10 278h-27Fh, 678h-67Ah
11 -reserved-
1
Enable
1-0 Sound Blaster Decode Range
00 220h-22Fh, 230h-233h .......................... default
01 240h-24Fh, 250h-253h
3
2
Game Port Positive Decoding
0
1
Disable ...................................................default
Enable
10 260h-26Fh, 270h-273h
11 280h-28Fh, 290h-293h
MIDI Positive Decoding
0
Disable ...................................................default
1
Enable
1-0 MIDI Decode Range
00 300h-303h ..............................................default
01 310h-313h
10 320h-323h
11 330h-333h
Revision 1.71 June 9, 2000
-65-
Function 0 Registers - PCI to ISA Bridge
ETC [ ETC ]
