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CRC calculation

This page explains how to obtain the proper CRC value of the MCB protocol.

CRC description (CRC-CCITT "XMODEM")

Parameter

Value

Width

16 bits

Polynomial

0x1021

Initial value (seed)

0x0000

Example

The example consist in a write command to the position set-point parameter and a read command on the velocity actual value. 

CRC calculation on SPI based protocols (transfer done in word size)

Simple write example

Write access to register 0x20 (position set-point) with a value of 100000

Header

Config data

CRC

Address

Command

Pending frame

0x020

0b010

0

0x186A0

0xA2C7

0x0204186A0000000000000A2C7

Successful reply

Header

Config data

CRC

Address

Command

Pending frame

0x020

0b011

0

0x0

0xB5D8

0x02060000000000000000B5D8



Simple read example

Read access to register 0x31 (velocity actual) with a value of 1000.0

Header

Config data

CRC

Address

Command

Pending frame

0x010

0b001

0

0

0x6758

0x031200000000000000006758

Successful reply

Header

Config data

CRC

Address

Command

Pending frame

0x010

0b011

0

0x447A0000

0x919D

0x03160000447A00000000919D


CRC calculation on other protocols (transfer done in byte size)

Simple write example

Write access to register 0x20 (position set-point) with a value of 100000

Node ID

Header

Config data

CRC

Address

Command

Pending frame

0x0001

0x020

0b010

0

0x186A0

0xA1B2

0x01000402A086010000000000B2A1

Successful reply

Node ID

Header

Config data

CRC

Address

Command

Pending frame

0x0001

0x020

0b011

0

0x0

0xB6AD

0x010006020000000000000000ADB6



Simple read example

Read access to register 0x31 (velocity actual) with a value of 1000.0

Node ID

Header

Config data

CRC

Address

Command

Pending frame

0x0001

0x031

0b001

0

0

0x642D

0x0100120300000000000000002D64

Successful reply

Node ID

Header

Config data

CRC

Address

Command

Pending frame

0x0001

0x031

0b011

0

0x44A0000

0x92E8

0x0100160300007A4400000000E892