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Symmetric Key Hardware Accelerator (SKHA)
35.4.3
Operation with Context Switch
The intended operation to process part of one message, followed by an intermediate message, and resume
processing the original message is as follows:
1. Reset/initialize.
2. Set algorithm, set processing direction and cipher mode in the SKMR.
3. Write IV/Nonce to SKCn registers.
4. Write the symmetric key to SKKDRn registers.
5. Write the number of bytes in the key to SKKSR.
6. Set number of bits in the first part of message 1 in the SKDSR.
7. Load the input FIFO with first part of message 1.
8. Set the SKCMR[GO] bit.
9. Wait for done interrupt, SKSR[DONE].
10. Unload processed message data from the output FIFO.
11. Read context registers and store contents in memory.
12. Set the SKCMR[CI] bit, to clear the done interrupt.
13. Reset/initialize.
14. Process intermediate message as described in
15. Reset/initialize.
16. Set algorithm, processing direction and cipher mode in the SKMR.
17. Restore context registers from memory.
18. Restore symmetric key to SKKDRn.
19. Write number of bytes in the key to the SKKSR.
20. Set number of bits in remaining part of message 1 to SKDSR.
21. Load the input FIFO with the remaining portion of message 1.
22. Set the SKCMR[GO] bit.
23. Wait for interrupt, SKSR[INT].
24. Unload processed message data from the output FIFO.
35-20
Section 35.4.1, "General Operation"
MCF5329 Reference Manual, Rev 3
Freescale Semiconductor
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