User manual

PD-1160 TMCL Firmware V1.19 Manual (Rev. 1.01 / 2012-JUL-30) 14
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3.1.1 Checksum Calculation
As mentioned above, the checksum is calculated by adding up all bytes (including the module address
byte) using 8-bit addition. Here are two examples to show how to do this:
- in C:
unsigned char i, Checksum;
unsigned char Command[9];
//Set the “Command” array to the desired command
Checksum = Command[0];
for(i=1; i<8; i++)
Checksum+=Command[i];
Command[8]=Checksum; //insert checksum as last byte of the command
//Now, send it to the module
- in Delphi:
var
i, Checksum: byte;
Command: array[0..8] of byte;
//Set the “Command” array to the desired command
//Calculate the Checksum:
Checksum:=Command[0];
for i:=1 to 7 do Checksum:=Checksum+Command[i];
Command[8]:=Checksum;
//Now, send the “Command” array (9 bytes) to the module
3.2 Reply Format
Every time a command has been sent to a module, the module sends a reply.
The reply format for RS485/ /USB is as follows:
Bytes
Meaning
1
Reply address
1
Module address
1
Status (e.g. 100 means no error)
1
Command number
4
Value (MSB first!)
1
Checksum
- The checksum is also calculated by adding up all the other bytes using an 8-bit addition.
- When using CAN bus, just leave out the first byte (module address) and the last byte (checksum).
- Do not send the next command before you have received the reply!