Freescale Semiconductor MPC8313E Family Reference Manual page 658

Security Engine (SEC) 2.2
Field Name
DPD_DES_CTX_CRYPT
LEN_CTXIN
PTR_CTXIN
LEN_KEY
PTR_KEY
LEN_DATAIN
PTR_DATAIN
LEN_DATAOUT
PTR_DATAOUT
LEN_CTXOUT
PTR_CTXOUT
Null length
Null pointer
Null length
Null pointer
Each descriptor contains eight long-words (64 bits each), consisting of the following:
• One long-word of header—The header describes the required services and encodes information
that indicates which EUs to use and which modes to set. It also indicates whether notification
should be sent to the host when the descriptor operation is complete.
• Seven long-words containing pointers and lengths used to locate input or output data.
Upon completion of the current descriptor, the channel checks the next entry in its fetch FIFO, and, if
non-zero, the channel is instructed to request a burst read of the next descriptor.
Processing of the next descriptor (and whether or not a done signal is generated) is determined by the
programming of channel's configuration register. Two modes of operation are supported:
• Signal done at end of every descriptor
• Signal done at end of a selected descriptor
The channel can signal done through an interrupt, or by a write-back of to descriptor header in non-SEC
memory after processing a descriptor. Either the value written back is identical to that of the header, with
the exception that a DONE field is set, or special status fields are written back. That status writeback field
can be reserved for descriptors performing ICV checking.
Occasionally, a descriptor field may not be applicable to the requested service. For example, if using DES
in ECB mode, the contents of the IV field do not affect the result of the DES computation. Therefore, when
processing descriptors, the channel skips any pointer that has an associated length of zero.
For more information, refer to
MPC8313E PowerQUICC II Pro Integrated Processor Family Reference Manual, Rev. 3
14-4
Table 14-1. Example Descriptor
Value/Type
Variable Representative header for DES using context to encrypt
Length Number of bytes to be written
Pointer Pointer to context (IV) to be written into DES engine
Length Number of bytes in key
Pointer Pointer to block cipher key
Length Number of bytes of data to be ciphered
Pointer Pointer to data to perform cipher upon
Length Number of bytes of data after ciphering
Pointer Pointer to location where cipher output is to be written
Length Length of output context (IV)
Pointer Pointer to location where altered context is to be written
Length Zeros for fixed length descriptor
Pointer Zeros for fixed length descriptor
Length Zeros for fixed length descriptor
Pointer Zeros for fixed length descriptor
Section 14.3, "Descriptor Overview."
Description
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