82801DB Datasheet, PDF (473/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

AC ’97 Audio Controller Registers (D31:F5)
14.1.11 NABMBAR—Native Audio Bus Mastering Base Address
Register (Audio—D31:F5)
Address Offset:
Default Value:
Lockable:
14–17h
00000001h
No
Attribute:
Size:
Power Well:
R/W, RO
32 bits
Core
The Native PCI Mode Audio function uses PCI Base Address register #1 to request a contiguous
block of I/O space that is to be used for the Native Mode Audio software interface.
Note: The DMA registers for S/PDIF and Microphone In 2 cannot be addressed via this address space.
These DMA functions are only available from the new MBBAR register. This register powers up
as read only and only becomes write-able when the IOSE bit in offset 41h is set.
Bit
31:16
15:6
5:1
0
Description
Hardwired to 0s
Base Address — R/W. These bits are used in the I/O space decode of the Native Audio Bus
Mastering 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 AC '97 bus mastering, the upper
16 bits are hardwired to 0, while bits 15:6 are programmable. This configuration yields a maximum
I/O block size of 64 bytes for this base address.
Reserved. Read as 0s.
Resource Type Indicator (RTE) — RO. This bit is set to 0, indicating a request for I/O space.
14.1.12
MMBAR—Mixer Base Address Register (Audio—D31:F5)
Address Offset:
Default Value:
Lockable:
18–1Bh
00000000h
No
Attribute:
Size:
Power Well:
R/W, RO
32 bits
Core
This BAR creates 512 bytes of memory space to signify the base address of the register space. The
lower 256 bytes of this space map to the same registers as the 256-byte I/O space pointed to by
NAMBAR. The lower 384 bytes are divided as follows:
• 128 bytes for the primary codec (offsets 00–7Fh)
• 128 bytes for the secondary codec (offsets 80–FFh)
• 128 bytes for the tertiary codec (offsets 100–17Fh).
• 128 bytes of reserved space (offsets 180–1FFh), returning all 0s.
Bit
Description
31:9
Base Address — R/W Lower 32-bits of the 512-byte memory offset to use for decoding the
primary, secondary, and tertiary codec’s mixer spaces.
8:3 Reserved. Read as 0s.
2:1 Type — RO. Indicates the base address exists in 32-bit address space
0
Resource Type Indicator (RTE) — RO. Hardwired to 0, indicating a request for memory space.
Intel^® 82801DB ICH4 Datasheet
473