[Gmecm] What really is a 'mask'?

[Don Sauman]

My understanding is that the mask is that part a program on a ROM that 
is created during manufacture for a specific purpose and cannot be 
erased. I.e. non-volatile memory.

Don

davesnothereman at netscape.net wrote:

> From what I understand, the mask ID is a calculated number.  I believe the table locations and sizes as well as code length are the main contributors to the ID.  Ludis Langens wrote a program several years ago which would look at a calibration and calculate the mask ID, as well as determine whether the file was stock or modified, and if stock would return the BCC.
> 
>The BCC is the broadcast code, an identifier used to pick out specific calibrations as mandated by US law.  While the mask can be thought of as the "table location and code template," the various BCC's associated with a certain mask represent different calibration variables.
> 
>The mask ID system does not guarantee a unique identifier for every variation of code and table.  Ludis had mentioned once that there are different codes which will generate the same mask ID.
> 
>Since a similar question has come up on another list, I have been thinking about this.  I wonder if the term "mask" has a historical reference to the early days of prom production.
> 
>Zaphod
> 
> 
>-----Original Message-----
>From: Robin at FuryWorld.fsnet.co.uk
>To: gmecm at diy-efi.org
>Sent: Sat, 2 Sep 2006 2:28 PM
>Subject: [Gmecm] What really is a 'mask'?
>
>
>I've never really known what a GM software 'mask' is - never having seen a
>clear definition of it. I had been beginning to think, of late, that a
>'mask' (e.g. $58, $8D) is a particular version of GM code, which is used in
>different applications (and given different 4-latter designations e.g.
>ANHT/AUJP) by changing the calibration data only. But now I'm not so sure.
>Could somebody clarify?
>
>Robin
>
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>  
>

-- 
Don Sauman
Cythera Communication
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