# How does CRC work?

## 9. Various CRC algorithms

How does CRC work? Chapter 9 Various CRC algorithms Chapter 9.1 Introduction The basis of all algorithms is Chapter 4 CRC arithmetic. In Chapter 5 Calculating CRC on registers we showed how to implement this single-bit shift algorithm on registers. Programmers of microprocessor systems do not use bits but bytes, and this is what the …

## 8. What if we shifted by 8 bits?

How does CRC work? Chapter 8 What if we shifted by 8 bits? Chapter 8.1 Introduction You will find that 8-bit shifts are very similar to the 2-bit shifts from the previous chapter. The ratio is almost 1:1, i.e. instead of 2-bit shifts, they are 8-bit, and the CRC itself can be 8, 16 or …

## 7. What if we shifted by 2 bits?

How does CRC work? Chapter 7 What if we shifted by 2 bits? Chapter 7.1 Introduction We know from the previous chapter that the actual CRC register is 1, 2, or 4 bytes long. And what else is it different from the one in chapter 5? First of all, shifts. In earlier chapters they were …

## 6. CRC size and the ability to detect transmission errors

How does CRC work? Chapter 6 CRC size and the ability to detect transmission errors  In the previous chapter, the CRC register had 4 bits and the sent message was located in the 8-bits A register. You will probably agree, that the system would equally well calculate CRC for any multiple of 8 bits, i.e. …

## 5. Calculating CRC on registers

How does CRC work? Chapter 5 Calculating CRC on registers Chapter 5.1 Introduction You already know how to calculate CRC and it is much easier than simple decimal division. The algorithm is only shifts and possibly xor-ing. They can therefore be easily implemented on shift registers supported by simple logic based on xoring.ig. 5-1 Chapter …

## 4. CRC Arithmetic

How does CRC work? Chapter 4 CRC Arithmetic Chapter 4.1 Introduction We will start with a topic that you already know from primary school, which is written division. Then you will see that calculating CRC is similar, only much simpler. You don’t have to wonder how many times “something” fits into “something”. There is nothing …

## 3. Logical Functions

How does CRC work? Chapter 3 Logical Functions Chapter 3.1 Introduction I have already mentioned that CRC is treated as a kind of “remainder” of division. The “division” is the message being sent, the “divisor” is a certain constant known to the Transmitter and the Receiver, and the “rest” is the CRC. Wait, what’s most …

## 2. Simple examples of CRC transmission

How does CRC work? Chapter 2. Simple examples of CRC transmission Chapter. 2.1 Introduction In Chapter. 1.3 the question was asked “How does the AIR register in London know that the information in RR in New York received, i.e. the number 38547, is different than 32547 that AIR sent from London?” For this purpose, the …

## 1. Introduction

How does CRC work? Chapter 1  Introduction Chapter 1.1 Introduction Everyone has encountered the message “CRC data error… and something else” at some point. This is an error that appears, for example, when transmitting data from a CD to a hard drive, or more generally – when exchanging data between two devices in the network. …

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