AMD Geode LX 800@0.9W - Manual (Page 530)

530 AMD Geode™ LX Processors Data Book
Security Block Register Descriptions 33234H
6.12.3.20 SB EEPROM Command (SB_EEPROM_COMM)
SB Memory Offset 800h
Type
R/W
Reset Value 00000000h
SB_EEPROM_COMM Register Map
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RSVD RSVD
HKD
SL KV EX WR ST
SB_EEPROM_COMM Bit Descriptions
Bit Name Description
31:8 RSVD Reserved.
7:6 RSVD Reserved. These bits are implemented but reserved for future use. When writing to this
register, software should set these bits to 0 and ignore them on read.
5 HKD Hidden Key Disable. Reset to 0. When set, this bit disables the hidden key by forcing
all of the bits to zero. This bit can be written to a 1 by software, but once set, it can only
be cleared by reset. Setting this bit also forces the Key Valid bit (bit 3) to 0.
4 SD Soft Lock. Reset to 0. When set, this bit locks the same debug functions locked by the
DBL bit (SB Memory Offset 80Ch[10:8]), and is displayed in the Access Control register.
This bit can be written to a 1 by software, but once set, it can only be cleared by reset.
3 KV Key Valid. Reset to 0. After reset, this bit is set automatically by the state machine to
indicate that the automatic load of the hidden key into the AES key register has com-
pleted and the key is now ready for use. No AES operations using the hidden key regis-
ter should be initiated before this bit is set. This bit is cleared by reset or by asserting the
Hidden Key Disable bit (bit 5).
2 EX Exception. The current access operation did not complete successfully. Note that this
bit may also be set after a reset if the initial read of the EEPROM control bytes or hidden
key did not complete successfully. This bit should only be set on a fatal hardware access
error. Write 1 to clear. If the exception occurs on the initial EEPROM read after reset, it
is assumed that no EEPROM is preset and the EEPROM interface is disabled. When
the interface is disabled, this bit is not clearable.
1 WR Write. When set, the EEPROM interface initiates a write operation to the EEPROM
when the START bit (bit 0) is set. When reset, the EEPROM interface initiates a read
operation when the START bit is set.
0 ST START. When set, this bit commands the EEPROM interface to start a new operation
based on the current Control register setting and the settings in the Address and Data
registers. This bit is reset automatically when the operation completes. Setting this bit
also clears the EEPROM Complete flag in the AES Interrupt register (SB Memory Offset
008h[18]) and in the SMI MSR register (MSR 58002002h[34]).