82801DB Datasheet, PDF (497/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

AC ’97 Modem Controller Registers (D31:F6)
15.1.10
MMBAR—Modem Mixer Base Address Register
(Modem—D31:F6)
Address Offset: 10–13h
Default Value: 00000001h
Attribute:
Size:
R/W, RO
32 bits
The Native PCI Mode Modem uses PCI Base Address register #1 to request a contiguous block of
I/O space that is to be used for the Modem Mixer software interface. The mixer requires 256 bytes
of I/O space. All accesses to the mixer registers are forwarded over the AC-link to the codec where
the registers reside.
In the case of the split codec implementation accesses to the different codecs are differentiated by
the controller by using address offsets 00h – 7Fh for the primary codec and address offsets
80h – FEh for the secondary codec.
Bit
Description
31:16 Hardwired to 0s
Base Address — R/W. These bits are used in the I/O space decode of the Modem interface
registers. The number of upper bits that a device actually implements depends on how much of the
15:8 address space the device will respond to. For the AC ‘97 Modem, the upper 16 bits are hardwired to
0, while bits 15:8 are programmable. This configuration yields a maximum I/O block size of
256 bytes for this base address.
7:1 Reserved. Read as 0s
0 Resource Type Indicator (RTE) — RO. This bit is set to 1, indicating a request for I/O space.
15.1.11
MBAR—Modem Base Address Register (Modem—D31:F6)
Address Offset: 14–17h
Default Value: 00000001h
Attribute:
Size:
R/W, RO
32 bits
The Modem function uses PCI Base Address register #1 to request a contiguous block of I/O space
that is to be used for the Modem software interface. The Modem Bus Mastering register space
requires 128 bytes of I/O space. All Modem registers reside in the controller, therefore cycles are
not forwarded over the AC-link to the codec.
Bit
Description
31:16
15:7
6:1
0
Hardwired to 0s
Base Address — R/W. These bits are used in the I/O space decode of the Modem interface
registers. The number of upper bits that a device actually implements depends on how much of the
address space the device will respond to. For the AC ‘97 Modem, the upper 16 bits are hardwired to
0, while bits 15:7 are programmable. This configuration yields a maximum I/O block size of 128
bytes for this base address.
Reserved. Read as 0s
Resource Type Indicator (RTE) — RO. This bit is set to 1, indicating a request for I/O space.
Intel^® 82801DB ICH4 Datasheet
497