87c257 eprom

0x3ffa xx xx yy yy zz zz

x and y is chk, y is inverted x, chk is from 0x0000 to 0x3fff... use some hex editor to calc chk

WORKED?

Im still having problems understanding what hcman said. he explained the XX YY but he has a ZZ in there too. he says nothing about what ZZ is. i also dont understand what is meant by Y is inverted X. it sort of made sense when i first read it but now after attempting it with failure i just dont get it. any help here?

thank you! could you explain the last 2 bits?

thank you  . now i understand completely. i wish more people would explain things like this in depth. im still sort of new to this ECU, ive been trying to understand it for like a year now and its by far the least documented version of motronic. I have one more question out of curiousity. is it possible to raise or flatten certain maps on the boost chip so that the N75 would no longer function and i could use a manual boost controller instead? also which maps would i modify to make this possible? its just an idea i had and atleast in my situation with a lack of knowledge of this ECU it would be easier for me to just set my boost manually and focus on learning the timing/fuel chip.