ATxmega128D4-AU ATMEL [ATMEL Corporation], ATxmega128D4-AU Datasheet - Page 45

• Manufacturer Part Number: ATxmega128D4-AU
• Description: 8/16-bit Atmel XMEGA D4 Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

24. CRC – Cyclic Redundancy Check Generator
24.1
24.2
8135L–AVR–06/12
Features
Overview
•
•
•
•
A cyclic redundancy check (CRC) is an error detection technique test algorithm used to find
accidental errors in data, and it is commonly used to determine the correctness of a data trans-
mission, and data present in the data and program memories. A CRC takes a data stream or a
block of data as input and generates a 16- or 32-bit output that can be appended to the data and
used as a checksum. When the same data are later received or read, the device or application
repeats the calculation. If the new CRC result does not match the one calculated earlier, the
block contains a data error. The application will then detect this and may take a corrective
action, such as requesting the data to be sent again or simply not using the incorrect data.
Typically, an n-bit CRC applied to a data block of arbitrary length will detect any single error
burst not longer than n bits (any single alteration that spans no more than n bits of the data), and
will detect the fraction 1-2
devices supports two commonly used CRC polynomials; CRC-16 (CRC-CCITT) and CRC-32
(IEEE 802.3).
• CRC-16:
• CRC-32:
Cyclic redundancy check (CRC) generation and checking for
Integrated with flash memory and CPU
CRC polynomial software selectable to
Zero remainder detection
– Communication data
– Program or data in flash memory
– Data in SRAM and I/O memory space
– Automatic CRC of the complete or a selectable range of the flash memory
– CPU can load data to the CRC generator through the I/O interface
– CRC-16 (CRC-CCITT)
– CRC-32 (IEEE 802.3)
Polynomial:
Hex value:
Polynomial:
Hex value:
x
0x1021
x
0x04C11DB7
16
32
-n
+x
+x
of all longer error bursts. The CRC module in Atmel AVR XMEGA
12
26
+x
+x
5
23
+1
+x
22
+x
16
+x
12
+x
11
+x
10
+
x
8
+x
7
+x
5
+x
4
+x
2
+x+1
XMEGA D4
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