82C931 Datasheet, PDF (37/64 Pages) List of Unclassifed Manufacturers – Plug and Play Integrated Audio Controller

82C931
5.0 Register Descriptions
5.1 I/O Base Addresses
Table 5-1 lists the I/O base address registers of the 82C931.
These base addresses are programmable, which assists in
avoiding possible I/O port conflicts among different devices.
The configuration registers, called MC Indirect Registers,
located via MCBase control most functions of the 82C931. An
indirect addressing scheme is used to access the MC Indirect
Registers.
The MC address (0E0Eh-0EFEh) and data (0E0Fh-0FFFh)
I/O port addresses are fully programmable. The only fixed I/O
port used by the 82C931 is at 0F8Dh.
The remaining I/O base address registers are accessed by
the same type of indexing scheme as MCBase (CPU Direct
I/O R/W).
Table 5-2 gives the register map of the 82C931.
5.2 MCBase Register
MCBase is the Direct MC base address register which con-
trols access to the MC Indirect Registers (MCIR1-23).
MCIR1-23 control most of the basic functions of the 82C931
(i.e., CD-ROM select, base decode address select, etc.).
To avoid possible conflict of I/O ports with different devices,
the 82C931 uses a unique indirect addressing scheme with
the base addresses being programmable. Under this design
scheme, the only fixed I/O port used by 82C931 is at 0F8Dh.
The MC address and data I/O port addresses are fully pro-
grammable, from 0E0Eh-0EFEh (address port) and 0E0Fh-
0FFFh (data port). To access the MC registers:
(1) All MC registers in 82C931 are password protected. To
read or write into the MC registers, the password E4h
must be written into I/O Port 0F8Dh before accessing the
address or data port.
(2) The address and data access port address can be fully
programmable by writing the desired base address
selection into I/O port 0F8Dh bit 4 to bit 0, [b4..b0]. The
port address can be read as ‘111b4, b3..b0, 1110’ for the
address port and ‘111b4, b3..b0, 1111’ for the data port.
Therefore, the possible address and data access ports
can be any one from 0E0Eh-0FFEh (address port) and
0E0Fh-0FFFh (data port).
Table 5-1
Base Register
MCBase
SBBase
WSBase
IDEBase
ALBase
OPL4Base
MIDIBase
82C931 I/O Base Addresses
Function
Configuration
Digital Audio Processor
Windows Sound System
IDE CD ROM
AdLib
OPL4
MPU-401
Address Selections
0F8D; 0E0[E..F] to
0FF[E..F]
220/240
530/640/E80/F40
170/370
388
380
300/310/320/330
Table 5-2 82C931 Register Map
I/O Address
SBBase+00h (or
ALBase+00h)
SBBase+00h (or
ALBase+00h)
SBBase+01h (or
ALBase+01h)
SBBase+02h (or
ALBase+02h)
SBBase+03h (or
ALBase+03h)
SBBase+04h
SBBase+05h
SBBase+06h
SBBase+08h
SBBase+08h
SBBase+09h
SBBase+0Ah
SBBase+0Ch
SBBase+0Ch
SBBase+0Eh
Register Name (Type)
Left FM Status Port (RO)
Left FM Register Address Port (WO)
Left FM Data Port (WO)
Right FM Register Address Port (WO)
Right FM Data Port (WO)
Mixer Address Port (WO)
Mixer Data Port (R/W)
DAP Reset (WO)
FM Status Port (RO)
FM Register Address Port (WO)
FM Data Port (WO)
DAP Read Data (RO)
DAP Write Data/Cmd (WO)
DAP Write Buffer Status (RO)
DAP Output Buffer Status (RO)
WSBase+00h-03h
WSBase+00h-03h
WSBase+04h
WSBase+05h
WSBase+06h
WSBase+07h
Configuration (WO)
Version (RO)
Codec Index Reg (R/W, exists in Codec and shad-
owed in 82C931)
Codec Indexed Data Reg (R/W, exists in Codec only)
Codec Status Reg (R/W, exists in Codec only)
Codec Direct Data (R/W, exists in Codec only)
200h-201h
Game Port (R/W)
0F8Dh
MCBase/Password Register - Specifies:
MC Index Port Address (R/W)
MC Data Port Address (R/W)
380-383/388-38B
388-38F
OPL4 (R/W)
OPL5 (R/W)
912-3000-035
Revision: 2.1
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