Data Sheet

Copyright © Roboteq Inc. 2018. All Rights Reserved. 10
'0' '1'
Node address – 0x01
'0' '4'
Function code (Read Input Registers) – 0x04
'2' '0' 'C' '1'
Register address for reading VAR1 – 0x20C1
'0' '0' '0' '2'
Length of registers to be read (must be 2) – 0x0002
'1' '8'
LRC
<CRLF>
End of message, carriage return and line feed – 0x0D0A
The response for this message will be as following:
:01040400001234DE<CRLF>
Name
Description
':'
Start of message - 0x3A
'0' '1'
Node address – 0x01
'0' '4'
Function code (Read Input Registers) – 0x04
'0' '4'
Read data length (4 bytes) – 0x04
'0' '0' '0' '0' '1' '2' '3' '4'
Value read from VAR1 – 0x00001234
'D' 'E'
LRC
<CRLF>
End of message, carriage return and line feed – 0x0D0A
2.3 Register Address Calculation
Register address is calculated based on CANOpen ID of the command/query. You can use the following
steps to get the register address.
- From Roboteq Manual find your command/query.
- Get the CANOpenID value.
- Left shift the CANOpenID with 5 bits.
- OR the result with the command/query index.
- AND the result with 0xFFFF.
- The resulting value will be the register address.
For example, the read user integer variable CANOpen ID is 0x2106 and suppose we are required to read
the first variable:
- CANOpenID = 0x2106
- Left shift with 5 → 0x2106 << 5 = 0x420C0
- OR with index → 0x420C0 | 0x01 = 0x420C1
- AND the result with 0xFFFF → 0x420C1 & 0xFFFF = 0x20C1
- Use 0x20C1 as the address.