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<DIV><FONT size=2>Does anyone know about checksums ?</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>I'm reverse engineering some CNC code and I can't seem to find
out how it works.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT
size=2>R22302230100000000049900000000B900000000F900031367D90000000040000000277F4F00<BR>R22302230100000000049900000000B900000000F900031367D900000000400000004F7F2700</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Note the format seems to be 8 digits and 2 code, so 99
B9 F9 D9 40 F4 are function codes. The 8 digits are the
numeric values. </FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>These are 2 lines of code. I think the last 2 non zero digits
are the checksums, 4F and 27.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>This is a drill command and the only differences between
commands is ones feed is 100 and the other 200. I think this is reflected
in 27 and 4F before the 7F. The is common to all CNC commands. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2>What is interesting is the Checksum for the first line is 4F
with a feed of 27 and the second is 27 with a feed of 47. By this I take
it they are using ones compliment checksum routines. </FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Any ideas ?</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>(Bring out those Commodore 64 programmers.)</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Cheers Wallace</FONT></DIV>
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