371
11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
22.4
Product Dependencies
22.4.1
Power Management
The CRCCU is clocked through the Power Management Controller (PMC), the programmer
must first configure the CRCCU in the PMC to enable the CRCCU clock.
22.4.2
Interrupt Source
The CRCCU has an interrupt line connected to the Interrupt Controller. Handling the CRCCU
interrupt requires programming the Interrupt Controller before configuring the CRCCU.
22.5
CRCCU Functional Description
22.5.1
CRC Calculation Unit description
The CRCCU integrates a dedicated Cyclic Redundancy Check (CRC) engine. When configured
and activated, this CRC engine performs a checksum computation on a Memory Area. CRC
computation is performed from the LSB to MSB bit. Three different polynomials are available
CCITT802.3, CASTAGNOLI and CCITT16, see the bitfield description,
, for details.
22.5.2
CRC Calculation Unit Operation
The CRCCU has a DMA controller that supports programmable CRC memory checks. When
enabled, the DMA channel reads a programmable amount of data and computes CRC on the fly.
The CRCCU is controlled by two registers, TR_ADDR and TR_CTRL which need to be mapped
in the internal SRAM. The addresses of these two registers are pointed at by the
CRCCU_DSCR register.
TR_ADDR defines the start address of memory area targeted for CRC calculation.
TR_CTRL defines the buffer transfer size, the transfer width (byte, halfword, word) and the
transfer-completed interrupt enable.
To start the CRCCU, the user needs to set the CRC enable bit (ENABLE) in the CRCCU Mode
Register (CRCCU_MR), then configure it and finally set the DMA enable bit (DMAEN) in the
CRCCU DMA Enable Register (CRCCU_DMA_EN).
When the CRCCU is enabled, the CRCCU reads the predefined amount of data (defined in
TR_CTRL) located at TR_ADDR start address and computes the checksum.
The CRCCU_SR register contains the temporary CRC value.
Table 22-1.
CRCCU Descriptor Memory Mapping
CRCCU Address
SRAM Memory
CRC0x0
---->
TR_ADDR
CRC0x4
---->
TR_CTRL
CRC0x8
---->
Reserved
CRC0xC
---->
Reserved
CRC0x10
---->
TR_CRC
Содержание SAM4S Series
Страница 44: ...44 11100B ATARM 31 Jul 12 SAM4S Series Preliminary ...
Страница 412: ...412 11100B ATARM 31 Jul 12 SAM4S Series Preliminary ...
Страница 1105: ...1105 11100B ATARM 31 Jul 12 SAM4S Series Preliminary ...
Страница 1142: ...1142 11100B ATARM 31 Jul 12 SAM4S Series Preliminary Figure 43 3 100 ball VFBGA Package Drawing ...
Страница 1143: ...1143 11100B ATARM 31 Jul 12 SAM4S Series Preliminary Figure 43 4 64 lead LQFP Package Drawing ...
Страница 1145: ...1145 11100B ATARM 31 Jul 12 SAM4S Series Preliminary Figure 43 5 64 lead QFN Package Drawing ...