CCEN=B_0x0, KEYLOCK=B_0x0, CCLOCK=B_0x0
MCE cipher context 2 configuration register
| CCEN | Cipher context enable 0 (B_0x0): If an enabled region selects CTXID=z bypass mode is selected by MCE 1 (B_0x1): If an enabled region selects CTXID=z with ENC=01 MCE selects with the stream cipher the information stored in MCE_CCzCFGR, MCE_CCzNR and MCE_CCzKEYR. If the enabled region selects ENC=10 or 11 instead MCE selects with the block cipher the key information stored in MCE_CCzKEYR. |
| CCLOCK | Cipher context lock Note: This bit is set once. If this bit is set, it can only be cleared to 0 if MCE is reset. Setting this bit forces KEYLOCK bit to 1. 0 (B_0x0): Writes to MCE_CCzCFGR and MCE_CCzNR registers are allowed 1 (B_0x1): Writes to MCE_CCzCFGR and MCE_CCzNR registers are ignored until next MCE reset. |
| KEYLOCK | Key lock Note: This bit is set once. If this bit is set, it can only be cleared to 0 if MCE is reset. 0 (B_0x0): Writes to MCE_CCzKEYR registers are allowed 1 (B_0x1): Writes to MCE_CCzKEYR registers are ignored until next MCE reset. |
| KEYCRC | Key CRC When KEYLOCK=0, KEYCRC information is automatically computed by hardware while loading the key of this region in this exact sequence: KEYR0 then KEYR1 then KEYR2 then finally KEYR3 (all written once). A new KEYCRC computation starts as soon as a new valid sequence is initiated. KEYCRC bitfield reads as zero until a valid sequence is completed (after it return the computed CRC value). When GLOCK=1, KEYCRC bitfield always return the computed CRC value until the next reset. CRC computation is an 8-bit checksum using the standard CRC-8-CCITT algorithm X8 + X2 + X + 1 (according the convention). Note: CRC information is updated, and the key is usable by MCE, only after the last bit of the key has been written. When GLOCK=0 any write to MCE_CCxKEYR registers clears KEYCRC in MCE_CCxCFGR, and makes the cipher context key un-usable (bypass mode is selected instead). To be able to use the key again application must perform this sequence: write to KEYR0 then KEYR1 then KEYR2 then finally KEYR3 (all written once). As KEYLOCK=1 all those writes are ignored, so the correct key is used instead. |
| VERSION | Version This 16-bit bitfield must be correctly initialized before CCEN bit is set. Bitfield usage is defined in Section 35.4.6: MCE stream cipher encryption mode. |