Too many BCCs, too few mask ids

[Programmer]

In every "doubled up" case, are the actual bins the same size, etc...??
Would
that be usefull in identifying things ?
Lyndon.
-----Original Message-----
From: Ludis Langens <ludis at cruzers.com>
To: gmecm <gmecm at diy-efi.org>
Date: November 19, 2000 1:41 PM
Subject: Too many BCCs, too few mask ids


>I'm writing a utility program that automates several things I often do
>with chip binaries.  I'll be releasing the program under a GNU license.
>One of the important features of this utility is identifying the mask
>id, scan id, and BCC of a binary.
>
>The mask id is determined by checksumming the chip's program code and
>table headers.  (The mask id byte in the chip is ignored in case it was
>set to experimental mode.)  Once the mask id is known, the scan id can
>be pulled out of the binary.  Possible BCC's are then determined from
>the scan id and mask id.
>
>This is where I'm running into problems.  The program has a huge table
>of BCC's along with their scan and mask id's.  However, I don't know the
>mask id of many of them.  Thus the BCC search function must match many
>BCC's by just the scan id.  Some scan id's are reused as many as ten
>times.  This means that sometimes I get several false matches.
>
>I have more information about each BCC than just it's scan id.  There
>ought to be a way of using this data to, for example, not offer up a
>carburetor BCC for a 1227730 binary.  In the mask identification stage,
>my data tables have space for a 32 bit mask id.  (Eight of those bits
>need to specify the value of the binary's mask id byte.)  In the BCC
>table, there is room for a 16 bit value.  What's needed is some sort of
>encoding in the spare bits that identifies the general type of binary.
>Any suggestions?
>
>Note: C3 ECM binaries in general don't have the unknown mask id problem
>- if I've gotten at least one binary for that ECM.  The mask ROM code of
>a C3 requires that all it's PROMs have the same mask id.
>
>There's another related problem which needs a solution.  Some mask id's
>have variants, or have been reused outright.  For example, there are
>multiple variations of the V8 TPI code, and the 3.8 V6 engine has one
>mask id (0x5b) reused at least three times for totally different code
>and once for a minor variation.  Further, GM ran out of mask id's and
>wrapped the byte value back around to small numbers.  How should the
>utility program report these reused mask id's to the user?  "5Baa, 5Bab,
>5Bb, and 5Bc", or "5B.1a, 5B.1b, 5B.2, 5B.3", "05B.1a, 05B.1b, 05B.2,
>15B", or something else?
>
>--
>Ludis Langens                               ludis (at) cruzers (dot) com
>Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
>
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