MSC8144E Reference Manual, Rev. 3
26-40
Freescale
Semiconductor
Security Engine (SEC)
End_of_Message register must be written. The value in the Data Size Register is used to
determine how many bits of the final message block (always 64) to process. Note that the
End_of_Message register has no data size, and during the write operation, the core processor data
bus is not read. Hence, any data value is accepted. Normally, a write operation with a zero data
value is performed. Reading from this register is not meaningful: it always returns a zero value
and does not generate any error. Writing to this register is the trigger that causes the DEU to
process the final block of a message, allowing it to issue a done interrupt.
26.4.2.9 DEU IV Register
For CBC mode, the initialization vector is written to and read from the DEU IV register. The
value of this register changes as a result of the encryption process and reflects the context of
DEU. Reading this memory location while the module is processing data generates an error
interrupt.
26.4.2.10 DEU Key Registers
The DEU uses three write-only key registers, K1, K2, and K3, to perform encryption and
decryption. In Single DES mode, only K1 is written and the value is simultaneously written to
K3, auto-enabling the DEU for 112-bit Triple DES if the Key Size Register indicates 2-key 3DES
is to be performed (key size = 16 bytes). To operate in 168-bit Triple DES, K1 must be written
first, followed by the write of K2, then K3. Reading any of these memory locations generates an
address error interrupt.
26.4.2.11 DEU FIFOs
The DEU uses an input FIFO/output FIFO pair to hold data before and after the encryption
process. Normally, the channels control all access to these FIFOs. For core processor-controlled
operation, a write to anywhere in the DEU FIFO address space enqueues data to the DEU input
FIFO, and a read from anywhere in the DEU FIFO address space dequeues data from the DEU
output FIFO.
Writes to the input FIFO go first to a staging register that can be written in byte, 4-byte, or 8-byte
units. When all 8 bytes of the staging register are written, the entire 8 bytes is automatically
enqueued into the FIFO. If any byte is written twice between enqueues, it causes an error
interrupt of type AE from the EU. Since the DEU data length should always be a multiple of 8
bytes, the last write should complete the 8-byte set. However, if there is any partial data set in the
staging register when the DEU End_of_Message Register is written, the partial data set is
automatically padded with zeros to a full 8 bytes and enqueued to the input FIFO.
The output FIFO is readable in byte, 4-byte, or 8-byte units. When all 8 bytes of the header are
read, that 8-byte set is automatically dequeued from the FIFO so that the next 8 bytes (if any)
becomes available for reading. If any byte is read twice between dequeues, it causes an error
interrupt of type AE from the EU.
Содержание MSC8144E
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Страница 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
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Страница 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
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