Atmel AVR XMEGA AU series User Manual

325
8331B–AVR–03/12
Atmel AVR XMEGA AU
• Bit 1:0 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always
write these bits to zero when this register is written.
25.5.2 STATUS
– AES Status register
•Bit 7
– ERROR: Error
The ERROR flag indicates an illegal handling of the AES crypto module. The flag is set in the fol-
lowing cases:
• Setting START in the control register while the state memory and/or key memory are not fully
loaded or read. This error occurs when the total number of read/write operations from/to the
STATE and KEY registers is not a multiple of 16 before an AES start.
• Accessing (read or write) the control register while the START bit is one.
This flag can be cleared by software by writing one to its bit location.
• Bit 6:1
– Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always
write these bits to zero when this register is written.
•Bit 0
– SRIF: State Ready Interrupt flag
This flag is the interrupt/DMA request flag, and is set when the encryption/decryption procedure
is completed and the state memory contains valid data. As long as the flag is zero, this indicates
that there is no valid encrypted/decrypted data in the state memory.
The flag is cleared by hardware when a read access is made to the state memory (the first byte
is read). Alternatively, the bit can be cleared by writing a one to its bit location.
25.5.3 STATE
– AES State register
The STATE register is used to access the state memory. Before encryption/decryption can take
place, the state memory must be written sequentially, byte-by-byte, through the STATE register.
After encryption/decryption is done, the ciphertext/plaintext can be read sequentially, byte-by-
byte, through the STATE register.
Loading the initial data to the STATE register should be done after setting the appropriate AES
mode and direction. This register can not be accessed during encryption/decryption.
Bit 76543210
+0x01 ERROR – – – – – –SRIFSTATUS
Read/WriteR/WRRRRRRR/W
Initial Value00000000
Bit 76543210
+0x02 STATE[7:0] STATE
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0

Atmel AVR XMEGA AU series Specifications

General

Brand	Atmel
Model	AVR XMEGA AU series
Category	Microcontrollers
Language	English