W83C553F Datasheet, PDF (66/159 Pages) Winbond – SYSTEM I/O CONTROLLER WITH PCI ARBITER

W83C553F
Electrical Specifications
ISA-to-PCI Address Decoder Control Register (default = 01h)
Type:
Read/Write
Bit Description:
Bits [7:4]:
Bit 3:
Bit 2:
Bit 1:
Bit 0:
IPATOM [3:0]. Top of Main Memory. Defines the top of memory for ISA memory space. ISA
memory accesses from 1 MByte to top of memory (except "hole") and above 16 MByte are
forwarded to the PCI bus.
Bit 7 Bit 6 Bit 5 Bit 4 Top of Memory
0
0
0
0
1 MByte
0
0
0
1
2 MByte
0
0
1
0
3 MByte
0
0
1
1
4 MByte
0
1
0
0
5 MByte
0
1
0
1
6 MByte
0
1
1
0
7 MByte
0
1
1
1
8 MByte
1
0
0
0
9 MByte
1
0
0
1
10 MByte
1
0
1
0
11 MByte
1
0
1
1
12 MByte
1
1
0
0
13 MByte
1
1
0
1
14 MByte
1
1
1
0
15 MByte
1
1
1
1
16 MByte
MBELBIOS. Low BIOS Memory Block Enable; 896-960 KByte (E0000-EFFFFh). When set to
"1", ISA memory accesses in this range are forwarded to the PCI bus. The LBIOSCSE bit
(UBCSA, configuration register 4Dh bit 6) overrides this bit.
MBEVGA. VGA Memory Block Enable; 640-768 KByte (A0000-BFFFF). When set to "1", ISA
memory accesses in this range are forwarded to the PCI bus.
MBE640. Memory Block Enable; 512-640 KByte (80000-9FFFFh). When set to "1", ISA
memory accesses in this range are forwarded to the PCI bus.
MBE512. Memory Block Enable; 0-512 KByte (0-7FFFFh). When set to "1", ISA memory
accesses in this range are forwarded to the PCI bus. This bit is set to "1" after reset.
WINBOND SYSTEMS LABORATORY
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