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©2008 Advanced Micro Devices, Inc.
LPC ISA Bridge (Device 20, Function 3)
AMD SB600 Register Reference Manual Proprietary Page 261
Register Name Offset Address
SPI_FakeID 1Ch
SPI_Cntrl0 Register- RW - 32 bits - [Mem_Reg 00h]
Field Name Bits Default Description
SPI_OpCode 7:0 00h When software uses the alternate program method to
communicate with the SPI ROM, this register contains the
OPCODE
TxByteCount 11:8 0h Number of bytes to be sent to SPI ROM
RxByteCount 15:12 0h Number of bytes to be received from the SPI ROM
ExecuteOpCode 16 0b Write 1 to execute the transaction in the alternate program
registers. Write 0 has no effect. When the transaction is
complete, this bit will return 0. If the command is an illegal
command, the bit cannot be set and thereby cannot execute
Reserved 18:17 00b
SpiArbEnable 19 1b If a MAC is sharing the ROM with the SB, both chips will need
to go through an arbitration process before either one can
access the ROM. This bit enables the arbitration. If MAC is not
sharing the SPI ROM, BIOS should set this bit to 0 to speed up
the SPI ROM access
FifoPtrClr 20 0b (write only) A write of 1 to this bit will clear the internal FIFO
pointer
FifoPtrInc 21 0b (write only ) A write of 1 to this bit will cause the internal FIFO
pointer to be incremented by 1
SpiAccessMacRomEn 22 1b This is a clear-once protection bit; once set, software cannot
access MAC’s portion of the ROM space (lower 512KB).
SpiHostAccessRomEn 23 1b This is a clear-once protection bit; once set, MAC cannot
access BIOS ROM space (upper 512KB)
ArbWaitCount 26:24 100b Under ROM sharing mode (with the MAC) this defines the
amount of wait time this controller will assert HOLD# before it
should access the SPI ROM. This time is to allow the MAC to
sample HOLD#.
SpiBridgeDisable 27 0b Setting this bit will disable the SPI bridge mode (SB600 will act
as a SPI-LPC bridge to the MAC)
Reserved 31:28 0h
SPI_RestrictedCmd1 Register- RW - 32 bits - [Mem_Reg 04h]
Field Name Bits Default Description
RestrictedCmd0 7:0 00h This defines a restricted command issued by the MAC which
will be checked by the SB600. If the opcode issued by the
MAC matches with this register and the address space is in the
BIOS space, this controller will simply ignore the command for
the case of bridge mode. For peer mode, the SPI controller will
jam the entire interface as an attempt to stop that transaction.
Note either SpiAccessMacRomEn and/or
SpiHostAccessRomEn bit is cleared, these registers become
read only and cannot be changed any more.
RestrictedCmd1 15:8 00h Same as RestrictedCmd0
RestrictedCmd2 23:16 00h Same as RestrictedCmd0
RestrictedCmd3 31:24 00h Same as RestrictedCmd0
SPI_RestrictedCmd2 Register- RW - 32 bits - [Mem_Reg 08h]
Field Name Bits Default Description
RestrictedCmd4 7:0 00h Same as RestrictedCmd0
RestrictedCmdWoAddr
0
15:8 00h Same as RestrictedCmd0 except this command does not have
address