GD32W51x User Manual
941
Enable register CAU_INTEN. Value 1 of the register enable the interrupts.
Input FIFO interrupt
The input FIFO interrupt is asserted when the number of words in the input FIFO is less than
four words, then ISTA is asserted. And if the input FIFO interrupt is enabled by IINTEN with
a 1 value, the IINTF is also asserted. Note if the CAUEN is low, then the ISTA and IINTF are
also always low.
Output FIFO interrupt
The output FIFO interrupt is asserted when the number of words in the output FIFO is more
than one words, then OSTA is asserted. And if the output FIFO interrupt is enabled by
OINTEN with a 1 value, the OINTF is also asserted. Note Unlike that of Input FIFO interrupt,
the value of CAUEN will never affect the situation of OSTA and OINTF.
27.8.
CAU suspended mode
It is possible to suspend a data block if another new data block with a higher priority needs to
be processed in CAU. The following steps can be performed to complete the
encryption/decryption acceleration of the suspended data blocks.
When DM A transfer is used:
1. Stop the current input transfer. Clear the DMAIEN bit in the CAU_DMAEN register.
2. When it is DES or AES, wait until both the input and output FIFO are both empty if the
input FIFO is not empty (IEM = 0), then write a word of data into CAU_DI register, do as
so until the IEM is checked to be 1, then wait until the BUSY bit is cleared, so that the
next data block will not be affected by the last one. Case of TDES is similar to that of AES
except that it does not need to wait until the input FIFO is empty.
3. Stop the output transfer by clearing the DMAOEN bit in the CAU_DMAEN register. And
disable the CAU by clearing the CAUEN bit in the CAU_CTL register.
4. Save the configuration, including the key size, data type, operation mode, direction, GCM
CCM phase and the key values. When it is CBC, CTR, GCM, GMAC, CCM, CFB or OFB
chaining mode, the initialization vectors should also be stored. When it is GCM, GMAC,
or CCM mode, the context switch registers CAU_GCMCCMCTXSx (x = 0..7) and
CAU_GCMCTXSx (x = 0..7) should also be stored.
5. Configure and process the new data block.
6. Restore the process before. Configure the CAU with the parameters stored before, and
prepare the key and initialization vectors, and the context switch registers
CAU_GCMCCMCTXSx (x = 0..7) and CAU_GCMCTXSx (x = 0..7) should also be
restored. Then enable CAU by setting the CAUEN bit in the CAU_CTL register.
Содержание GD32W515 Series
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