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AMD Geode™ LX Processors Data Book 525
Security Block Register Descriptions
33234H
6.12.3.9 SB Length B (SB_LENGTH_B)
6.12.3.10 SB Writable Key 0 (SB_WKEY_0)
SB Memory Offset 028h
Typ e R /W
Reset Value 00000000h
SB_LENGTH_B 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
LENGTH_B RSVD
SB_LENGTH_B Register Bit Descriptions
Bit Name Description
31:4 LENGTH_B Length B. The Length field is a 32-bit value that describes the number of bytes to be
encrypted or decrypted in the next operation using pointer set B. The lower four bits
must be written as zero and always read zero. This forces the data length to be an inte-
ger number of 16-byte blocks. This register should not be changed during an AES
encryption or decryption operation using the A pointer set (i.e., while STA is asserted,
SB Memory Offset 000h[0] = 1). This register can be modified during an operation using
the B pointer set (while STB is asserted, SB Memory Offset 004h[0] = 1).
3:0 RSVD Reserved. Set to 0.
SB Memory Offset 030h
Typ e WO
Reset Value 00000000h
SB_W_KEY0 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
W_EY_0[31:0]
SB_WKEY_0 Bit Descriptions
Bit Name Description
31:0 WKEY_ 0 Writable Key 0. Bits [31:0] of the Writable Key for the Security Block. This register
should not be changed during an AES encryption or decryption operation. To prevent
one process from reading the key written by another process, this register is not read-
able.