AT90SCR100 datasheet(341/433 Pages) ATMEL

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TPR0327AY–SMS–30Jan09

AT90SCR100

25.3

AES Registers description

25.3.1

AESCR - AES Control Register

• Bit 7 - AESIE : AES Interrupt Enable

Set (one) this bit to enable interrupt generation when AES operation is ended.

Clear (zero) this bit to disable AES interrupt generation.

• Bit 6 - AESIF : AES Interrupt Flag

This bit is set by hardware on AES operation completion. If AESIE and SREG.I are set, an inter-

rupt is automatically generated.

This bit must be cleared by software.

• Bit 5 - AUTOKEY : Encrypt/Decrypt Automatic Key Generation Mode

This bit is set and cleared by software.

If this bit is set, when AESGO is set, a decryption (encryption) key is automatically generated

from the encryption (decryption) key and will be used in the decryption (encryption) operation.

This key is available in the key internal register and can be read.

If this bit is cleared, then AESGO performs a standard operation, using the key in its buffer.

• Bit 4 - KEYGN : Key Generation Mode

This bit is set and cleared by software.

This bit allows a decryption key to be generated from an encryption key without processing AES

data (which means that AES data registers won’t change).

When in this mode, a decryption key will be calculated from an encryption key if the ENCRYPT

bit is set and an encryption key will be calculated from a decryption key if the ENCRYPT bit is

cleared.

If this bit is set, AES key calculation will be perform when setting AESGO bit.

If this bit is cleared, AESGO bit will perform a standard operation, processing AES data.

• Bit 3 - KS : Key Selection bit

This bit is set and cleared by software.

Set this bit to activate AES256 mode, using 256 bits key.

Clear this bit to activate AES128 mode, using 128 LSB bits of the AES key (key[0..15]). The

MSB bits (key[16..31]) are unused.

• Bit 2 - Reserved bit

This bit is reserved for future use.

• Bit 1 - ENCRYPT : Encryption/Decryption bit

Bit

$0078

AESIE

AESIF

AUTOKEY

KEYGN

ENCRYPT

AESGO

AESCR

Read/write

R/W

Initial value

0x00

AT90SCR100 데이터시트(PDF) 341 Page - ATMEL Corporation

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