Debugging - Silicon Laboratories EFR32xG14 Wireless Gecko Reference Manual

Reference Manual
CRYPTO - Crypto Accelerator

31.4.10 Debugging

There are multiple ways of debugging CRYPTO sequences. The most straight-forward way is to write individual instructions to INSTR in
CRYPTO_CMD. An instruction can be written, and data can be read out and examined before running another instruction.
Running individual instructions to debug a program falls short when working with repeated sequences. In these cases, a sequence is
run multiple times over a set of data. This cannot be directly replicated with individual instructions
To debug a sequence, set HALT in CRYPTO_SEQCTRL. When set, CRYPTO requires software or the debugger to step it through each
instruction in the sequence. To step through the sequence, set SEQSTEP in CRYPTO_CMD. This will execute the current instruction,
and make CRYPTO ready to execute the next one.
When stepping through a sequence, the current instruction index can be read from SEQIP in CRYPTO_CSTATUS. SEQSKIP, also in
CRYPTO_CSTATUS tells whether the next instruction will be executed or not, based on previous conditionals in the program. SEQ-
PART in CRYPTO_CSTATUS shows whether CRYPTO is currently in part A or B of a sequence. Even with NOBUSYSTALL in CRYP-
TO_CTRL cleared, read and write accesses to CRYPTO will be allowed when CRYPTO is waiting to be stepped. This is to allow data
registers to be inspected during debugging.
Note: The data registers in CRYPTO (those marked read-actionable) require shifting of data in order to return the result. For this rea-
son, reading these registers will have no effect and will return unknown values during normal debugger read accesses (see 6.3.6 De-
bugger Reads of Actionable Registers).
31.4.11 Example: Cipher Block Chaining (CBC)
In the following the setup and operation of CBC is explained and illustrated. The example can easily be adjusted to perform other cipher
block modes.
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