> ## Documentation Index
> Fetch the complete documentation index at: https://notevil.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# CAPLfunctionJ1939SetChecksumAndCounter

# J1939SetChecksumAndCounter

[Valid for](../../../Shared/FeatureAvailability.md): CANoe DE • CANoe4SW DE

## Function Syntax

```
long J1939SetChecksumAndCounter(pg * msg, char[] calculationMethod, dword  counter)
```

## Description

This function calculates and sets the checksum of the given parameter group as well as the given counter. The available calculation algorithms are described in [J1939 Functional Safety – Messages With Integrated Checksum and Counter](../../../CANoeCANalyzer/J1939/j1939basics/j1939CrcAndCounter.md).

## Parameters

* **msg**: The parameter group to calculate and set the checksum for.
* **calculationMethod**: Two letters in the form \[A-E]\[a-f] (e.g. "Bc") that define the calculation rule and position of the checksum and message counter.
* **counter**: Current message counter to be set in the given parameter group.

## Return Values

* **0**: Checksum successfully filled.
* **-1**: Error: calculation method is invalid.

## Example

```c theme={null}
on key 'a'
{
  long err;
  pg * msg;
  dword counter = 0;

  msg.PGN = 0xF123; //DCDC4OS
  msg.SA = 0x1;
  msg.dlc = 8;
  msg.byte(0) = 0x01;
  msg.byte(1) = 0x02;
  msg.byte(2) = 0x03;
  msg.byte(3) = 0x04;
  msg.byte(4) = 0x05;
  msg.byte(5) = 0x06;
  msg.byte(6) = 0x07; // Bits 4-8 will be overwritten with the message counter
  msg.byte(7) = 0x08; // Will be overwritten with the checksum

  if(J1939SetChecksumAndCounter(msg, "Aa", counter) != 0)
  {
    write("Error while setting checksum and counter");
  }
  counter = (counter + 1) % 16;
  output(msg);
}
```