DVR21 datasheet(271/416 Pages) MICROCHIP

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 2016-2018 Microchip Technology Inc.

DS30010118D-page 271

PIC24FJ256GA705 FAMILY

22.0 32-BIT PROGRAMMABLE

CYCLIC REDUNDANCY CHECK

(CRC) GENERATOR

The 32-bit programmable CRC generator provides a

hardware implemented method of quickly generating

checksums for various networking and security

applications. It offers the following features:

• User-Programmable CRC Polynomial Equation,

up to 32 Bits

• Programmable Shift Direction (little or big-endian)

• Independent Data and Polynomial Lengths

• Configurable Interrupt Output

• Data FIFO

Figure 22-1 displays a simplified block diagram of the

CRC generator. A simple version of the CRC shift

engine is displayed in Figure 22-2.

FIGURE 22-1:

CRC BLOCK DIAGRAM

FIGURE 22-2:

CRC SHIFT ENGINE DETAIL

Note:

This data sheet summarizes the features of

this group of PIC24F devices. It is not

intended to be a comprehensive reference

source. For more information, refer to

the “dsPIC33/PIC24 Family Reference

Manual”,

“32-Bit

Programmable

Cyclic Redundancy Check (CRC)”

(DS30009729), which is available from the

Microchip website (www.microchip.com).

The information in this data sheet

supersedes the information in the FRM.

CRC

Interrupt

Variable FIFO

(4x32, 8x16 or 16x8)

CRCDATH

CRCDATL

Shift Buffer

CRC Shift Engine

CRCWDATH

CRCWDATL

Shifter Clock

2 * FCY

LENDIAN

CRCISEL

FIFO Empty

Event

Shift

Complete

Event

Note 1: n = PLEN<4:1> + 1.

CRC Shift Engine

CRCWDATH

CRCWDATL

Bit 1

Xn(1)

Read/Write Bus

Shift Buffer

Data

Bit 0

Bit n(1)

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