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94 Programmer’s Reference Manual
AC ’97 Modem Controller Registers (D30:F3)
3.1.11 MBAR—Modem Base Address Register (Modem—D30:F3)
Address Offset: 14h–17h Attribute: R/W, RO
Default Value: 00000001h Size: 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.
3.1.12 SVID—Subsystem Vendor Identification Register
(Modem—D30:F3)
Address Offset: 2Ch–2Dh Attribute: R/WO
Default Value: 0000h Size: 16 bits
Lockable: No Power Well: Core
The SVID register, in combination with the Subsystem ID register, enable the operating
environment to distinguish one audio subsystem from the other(s). This register is implemented as
write-once register. Once a value is written to it, the value can be read back. Any subsequent writes
will have no effect.
This register is not affected by the D3
HOT
to D0 transition.
Bit Description
31:16 Hardwired to 0’s.
15:7
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.
6:1 Reserved. Read as 0
0 Resource Type Indicator (RTE) — RO. Hardwired to 1 indicating a request for I/O space.
Bit Description
15:0 Subsystem Vendor ID — R/WO.