Chiptuning GM Vortec V6

chrisjost · Post by **chrisjost** » Mon Dec 01, 2003 3:12 am

Newly some days ago I made myself member in this interesting forum.
I found it in the search to information on possible modifications of the software like they are used in The Chevrolet Blazer with Flash 28F400.

My questions with regard to the adjustment of the Checksum:
- in what direction can it be made
- how do I calculate it
- which is the formula
- is there a program to do it
- with what the changes are to be multiplyed .

hoping that you can help me find the answers.

Chris Jost Argentine

Post by **Mangus** » Mon Dec 01, 2003 11:23 am

I'm unsure what exactly you're trying to do, but GM checksums are usually the LSW (least significant word) of the sum of the bytes from just beyond the checksum itself to the end of the bin.

if your checksum lives at offsets 6 and 7, for instance, then checksum is calculated from offset 8 through the end of the bin, and is stored at offset 6 and 7. If the sum of the bytes is, say, AABBCCDD, the checksum is CCDD.

If you know where the checksum lives in your binary, you can use TunerPro to calculate it.

chrisjost · Post by **chrisjost** » Mon Dec 01, 2003 12:06 pm

Hello! Thanks for the fast answer. TunerPro one can use only to 1Mb. In the Vortec engines is used one Flash 4Mb i. After changes in the characteristic diagram the Checksum must again be adapted. Therefore I look for these information those software have 8 different check around I white only the this starting from management 8000 am settled.

chris

Post by **Mangus** » Mon Dec 01, 2003 12:56 pm

the next version will have unlimited bin size.

your english makes it a little hard to figure out exactly what you're saying, so if you prefer to write in spanish, feel free.

chrisjost · Post by **chrisjost** » Mon Dec 01, 2003 12:57 pm

sorry , another one......
Can I send to you a file? and can you show me please the direction of add the checksum?
*checkSumAddr =
/*checkSumSize =
/*checkSumStartAddr =
/*checkSumEndAddr =

excuses please the annoyances.

chris

chrisjost · Post by **chrisjost** » Mon Dec 01, 2003 1:06 pm

sorry for my bad english.
I.m a german .

ok , lo hacemos en español , espero asi me entiendes un poco mejor.

como te dije recien me gustaria que te puede mandar un file de un Blazer V6 4.3 Vortec. tal vez me puedes encenniar en que direccion se encuentra la posibilidad de ajuste del checksum despues de unos cambios en el avance y al limitador del giro.

muchos saludos y muchas gracias para tu paciencia.

chris

chrisjost · Post by **chrisjost** » Tue Dec 02, 2003 12:59 pm

El problema es el siguiente, estoy acostumbrado a corregir el checksum en las direcciones $0006 y $0007 tomando el valor de $0008 hasta $7FFF (memoria 27c256), alli pongo el resultado en 16 bits y da todo correcto.

Ahora bien, en el caso de la 28f400bx, yo compare varios files y uno de los checksum corrige en la direccion $8000 .
Quisiera saber cual es el block de memoria que usa esa memoria para hacer el calculo de este checksum.

saludos Chris

Post by **Mangus** » Tue Dec 02, 2003 6:27 pm

Chris -

So your checksum should be calculated from 0x08 through 0x7FFF. I'm not sure what you mean when you say that you compare several files and one of them gets corrected in $8000.

in the case of GM, a single checksum should be used for the entire block of memory from just beyond the checksum itself (0x08) through the end of the file (0x7FFF). and the least significatn 16 bites should be stored at 0x06 through 0x07.

make sense?

chrisjost · Post by **chrisjost** » Wed Dec 03, 2003 4:38 am

Si, ese es el ejemplo de las memorias 27C256
En caso de las flash 28F400 ......... corrigem en el 2º block en la direccion $8000.

te puedo mandar un file del 28F400 ??

chris

Post by **Mangus** » Wed Dec 03, 2003 12:33 pm

You only checksum the block that contains the chips binary information. you don't checksum the entire chip.

so if your car uses a 16k chip, you only calculate the checksum for the 16k that the car uses ( $0008 through $3FFF ), even if the binary information lives in the highest memory block of a 29F040.

This is confusing stuff. The best thing to do is let TunerPro calculate it for you. just setup the checksum to live at $0006, 2 byte size, starting from $0008 through $3FFF.

Cmax · Post by **Cmax** » Wed Dec 03, 2003 1:00 pm

Hola Chris !!!

Yo hago tuning en Sao Paulo - Brasil y tengo el mismo problema, aqui hay muchas GM Vortec con memoria 28f400bx y no consigo acertar el checksum.
Tambien compare los internos de la memoria y recien en la direccion $8000 en adelante hacen el calculo del checksum cuando varian las curvas de nafta o avance.
Por lo que lei , estas memorias tienen 8 checksums diferentes .......
Si quieres me pasas tu mail y te envio los files que tengo para que los veas.

Un abrazo !!

Cmax

chrisjost · Post by **chrisjost** » Wed Dec 03, 2003 1:21 pm

Hola Cmax ! Muchas gracias para contestar. Como puedes observar estamos un poco complicado con el tema ....
mi e-mail : mecasport@arnet.com.ar
esperamos que participan mas personas para que encontramos la solucion. salu2 chris

Post by **Mangus** » Wed Dec 03, 2003 3:38 pm

ah, so the vortec code bases use multiple checksums? i see now. thats a different problem altogether. TunerPro does not support this kind of thing yet, but is planned a number of months down the road.