VT82C686B
Offset 48 - Miscellaneous Control 3.................................RW
4C - ISA DMA/Master Memory Access Control 1 ........ RW
........................................ always reads 0
7-4 Reserved
7-0 PCI Memory Hole Bottom Address
These bits correspond to HA[23:16] ............default=0
3
2
1
0
Extra RTC Port 74/75 Enable
0
Disable ...................................................default
4D - ISA DMA/Master Memory Access Control 2 ........ RW
1
Enable
(HA[23:16])
7-0 PCI Memory Hole Top Address
Integrated USB Controller Disable
These bits correspond to HA[23:16] ............default=0
0
Enable.....................................................default
1
Disable
Note: Access to the memory defined in the PCI memory
hole will not be forwarded to PCI. This function is
disabled if the top address is less than or equal to the
bottom address.
Integrated IDE Controller Disable
0
Enable.....................................................default
1
Disable
512K PCI Memory Decode
4F-4E - ISA DMA/Master Memory Access Control 3... RW
0
1
Use Rx4E[15-12] to select top of PCI memory
Use contents of Rx4E[15-12] plus 512K as top
of PCI memory.......................................default
for ISA DMA/Master accesses
15-12 Top of PCI Memory
0000 1M .................................................... default
0001 2M
... ...
1111 16M
Offset 4A - IDE Interrupt Routing ..................................RW
7
Wait for PGNT Before Grant to ISA Master /
DMA
Note: All ISA DMA / Masters that access addresses higher
than the top of PCI memory will not be directed to the
PCI bus.
0
Disable ...................................................default
1
Enable
6
Bus Select for Access to I/O Devices Below 100h
........def=0
.......def=0
........def=1
........def=1
......def=0
......def=0
.......def=0
.......def=0
.....def=0
11 Forward E0000-EFFFF Accesses to PCI
10 Forward A0000-BFFFF Accesses to PCI
0
1
Access ports 00-FFh via XD bus............default
Access ports 00-FFh via SD bus (applies to
external devices only; internal devices such as
the mouse controller are not effected)
9
8
7
6
5
4
3
2
1
0
Forward 80000-9FFFF Accesses to PCI
Forward 00000-7FFFF Accesses to PCI
Forward DC000-DFFFF Accesses to PCI
Forward D8000-DBFFF Accesses to PCI
Forward D4000-D7FFF Accesses to PCI
Forward D0000-D3FFF Accesses to PCI
Forward CC000-CFFFF Accesses to PCI
Forward C8000-CBFFF Accesses to PCI
Forward C4000-C7FFF Accesses to PCI
Forward C0000-C3FFF Accesses to PCI
..................... default = 0
5-4 Reserved (do not program)
3-2 IDE Second Channel IRQ Routing
00 IRQ14
01 IRQ15.....................................................default
10 IRQ10
11 IRQ11
......def=0
.......def=0
.......def=0
1-0 IDE Primary Channel IRQ Routing
00 IRQ14.....................................................default
01 IRQ15
10 IRQ10
11 IRQ11
Revision 1.71 June 9, 2000
-58-
Function 0 Registers - PCI to ISA Bridge
ETC [ ETC ]
