SEC Lite Crypto-Channel
MPC885 PowerQUICC Family Reference Manual, Rev. 2
50-12
Freescale Semiconductor
50.1.5
Descriptor Buffer (DB)
The descriptor buffer (DB) actually consists of 32 word aligned registers, and contains the current
descriptor being processed by the crypto-channel. This field is R/W enabled, however in typical operation,
the DB is filled by a write from the SEC Lite controller, acting as an initiator on the 8xx bus. (In host
controlled mode, the host processor can write the entire descriptor to the DB rather than creating the
descriptor in memory.)
The first word of the DB contains the header of the descriptor under processing. The DB uses information
in the descriptor header to request and program other on-chip resources in order to complete the required
security operation.
Words 2–15 contain fields for data length/data pointer pairs. Each pair consists of a length register, which
specifies the size if the data in bytes, and a pointer register which specifies the address of the first byte of
the data in system memory space.
Word 16 contains an extra register referred to as the “Next Descriptor Pointer” register, which contains a
pointer to the ‘next descriptor’ to be processed, if any. The pointer is set to zero for a single descriptor or
the end of a multi-descriptor chain. A descriptor is considered DONE only when the contents of word 16
have been processed by the channel. Additional information on the descriptor format and field values can
be found in
Chapter 49, “SEC Lite Descriptors.”
Figure 50-6. Data Packet Descriptor Buffer
50.1.5.1
Descriptor Header
Descriptors are created by the host to guide the SEC Lite through required crypto-graphic operations. The
descriptor header defines the operations to be performed, mode for each operation, and internal addressing
0
31
Word 1
Descriptor Header
Word 2
Length 1 (Key Length)
Word 3
Pointer 1 (Key Location)
Word 4
Length 2 (IV Length)
Word 5
Pointer 2 (IV Location)
Word 6
Length 3 (Data-in Length)
Word 7
Pointer 3 (Data-in Location)
Word 8
Length 4 (Data-Out Length)
Word 9
Pointer 4 (Data-out Location)
Word 10
Length 5 (NULL)
Word 11
Pointer 5 (NULL)
Word 12
Length 6 (NULL)
Word 13
Pointer 6 (NULL)
Word 14
Length 7 (NULL)
Word 15
Pointer 7 (NULL)
Word 16
Next Descriptor Pointer
Address
0x02080
Summary of Contents for PowerQUICC MPC870
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