Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Scheda Tecnica

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SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

The BTSIZE field located in the TR_CTRL register (located in memory), is automatically decremented if its value is
different from zero. Once the value of the BTSIZE field is equal to zero, the CRCCU is disabled by hardware. In this case,
the relevant CRCCU DMA Status Register bit, DMASR, is automatically cleared.

If the COMPARE field of the CRCCU_MR register is set to true, the TR_CRC (Transfer Reference Register) is compared
with the last CRC computed. If a mismatch occurs, an error flag is set and an interrupt is raised (if unmasked).

The CRCCU accesses the memory by single access (TRWIDTH size) in order not to limit the bandwidth usage of the
system, but the DIVIDER field of the CRCCU Mode Register can be used to lower it by dividing the frequency of the
single accesses.

The CRCCU scrolls the defined memory area using ascending addresses.

In order to compute the CRC for a memory size larger than 256 Kbytes or for non-contiguous memory area, it is possible
to re-enable the CRCCU on the new memory area and the CRC will be updated accordingly. Use the RESET field of the
CRCCU_CR register to reset the CRCCU Status Register to its default value (0xFFFF_FFFF).

Note:

These Registers are memory mapped

CRCCU_DSCR + 0x0

CRCCU Transfer Address Register

TR_ADDR

Read-write

CRCCU_DSCR + 0x4

CRCCU Transfer Control Register

TR_CTRL

Read-write

CRCCU_DSCR + 0xC - 0x10

Reserved

CRCCU_DSCR+0x10

CRCCU Transfer Reference Register

TR_CRC

Read-write