SWCU194 March 2023 CC1314R10 , CC1354P10 , CC1354R10 , CC2674P10 , CC2674R10
The following software example in pseudocode describes the actions that are typically executed by the host software to encrypt (using a basic AES mode) a message, stored in external memory, and place an encrypted result into a pre-allocated area in the external memory.
// configure the master control module
write ALGSEL 0x00000002 // enable the DMA path to the AES engine
write IRQCLR 0x00000001 // clear any outstanding events
// configure the key store to provide pre-loaded AES key
write KEYREADAREA 0x00000000 // load the key from ram area 0 (NOTE: The key
// must be pre-loaded to this area)
wait KEYREADAREA[31] == ’0’ // wait until the key is loaded to the AES module
check IRQSTAT[29] = ‘0’ // check that the key is loaded without errors
// Write the IV for non-ECB modes
// The IV must be written with the same conventions as the data
// if ((not ECB mode) and (not IV reuse))
// then: write the initialization vector when a new IV is required
write AESIV_0
...
write AESIV_3
// endif
// configure AES engine
write AESCTL = 0b0010_0000_0000_0000_0000_0000_0010_1100 // Program AES-CBC-128 encryption
// and save IV
write AESDATALEN0 // write length of the message (lo)
write AESDATALEN1 // write length of the message (hi)
write DMACH0CTL 0x000000001 // enable DMA channel 0
// configure DMAC
write DMACH0EXTADDR <address> // base address of the input data in ext.memory
write DMACH0LEN <length> // input data length in bytes, equal to the
// message length (may be non-block size aligned)
write DMACH1CTL 0x000000001 // enable DMA channel 1
write DMACH1EXTADDR <address> // base address of the output data buffer
write DMACH1LEN <length> // output data length in bytes, equal to the
// result data length (may be non-blocksize aligned)
// wait for completion
wait IRQSTAT[0] == ’1’ // wait for operation completed
check IRQSTAT[31] == ‘0’ // check for absence of errors
write AESALGSEL 0x00000000 // disable master control/DMA clock
// if (not ECB mode)
// then: only if the IV needs to be re-used/read
wait AESCTL[30] == ’1’ // wait for SAVED_CONTEXT_RDY bit [30]
read AESIV_0
...
read AESIV_3 // this read clears the SAVED_CONTEXT_RDY flag
// endif
// end of algorithm