Motion Page Checksum

[JavaRN]

Can anyone tell me how to compute the checksum for motion pages?

Right now I am working on a simple utility (in Java) that will allow me to move and mirror pages using the *.mtn file. The program seems to work ok i.e. pages are all saved in the file(including the mirrored and copied ones). However when I try to load the mtn file into the CM-5 the pages that are mirrored do not appear. It is as if they don't exist!

What I suspecting is that since I did not compute the checksum (I don't know the algorithm!) the loading program is ignoring the new pages and so they are not loaded.

Any help is greatly appreciated. Thanks

Charles

[Bullit]

Here you go. Its a simple 8 bit checksum that doesn't count the checksum itself which happens to be at address 31.

Code: Select all

byte ComputePageCheckSum(byte *bytePtr,word bytes)
{
  byte b=0;
  word addr;
   
  for(addr=0;addr<bytes;addr++)
    {
    if(addr != 31) //skip checksum byte
      {
      b = b + *bytePtr;
      }
    bytePtr++;
    }
  b = 0xff - b;
  return b;
}


for structure content if you're not already aware
http://forums.tribotix.info/forum1/76.html

[JavaRN]

Thanks a lot. Regarding the motion page structure I got info form there and here and manage to compile it - Thanks again.

[StuartL]

To calculate the checksum just zero the checksum byte and sum the remainder. Invert the result and place that in byte 31.

To check the checksum sum all bytes in the page and check to see if they total 0xff.