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serofast effect
May 9, 2017 11:18
7 yrs ago
anglais term

don’t care bits

anglais vers français Technique / Génie TI (technologie de l'information) Internet des objets
Only A12...A0 are used; the upper three address bits are don’t care bits.
Proposed translations (français)
4 +1 bits "dont' care" (quelconques)
4 -1 bit quelconque / bit X
3 bits sans effet

Discussion

Thomas T. Frost May 9, 2017:
This looks like matching What you describe here looks like wildcard bits (don't care/X/quelconque), not bits "sans effet".
Alain Boulé May 9, 2017:
When an adress bus comprises N bits out of which only M are used for address decoding the N-M are called don't care bits, as shows the document below:

Address decoders invariably decode regions that
start on an address that is a power-of-two. The
decoded region is invariably also a power-of-two.
Therefore the address range can be written as a bit
pattern that the decoder responds to. For example,
a decoder for addresses from 2 0000H to 2 7FFFH
( , 32 kBytes) would respond to addresses of
the form 0010 0XXX XXXX XXXX XXXX where
the X’s are “don’t cares.”

http://www.ece.ubc.ca/~edc/464/lectures/lec8.pdf
Thomas T. Frost May 9, 2017:
So they are not "don't care" bits In that case, Alain, the writer of the original text has misused the term "don't care" bits, it would seem, as "don't care" bits have a very specific meaning, as I have documented. This is something the translator ought to report back to the client and check. If indeed these are not real "don't care" bits, then "sans effet" would be correct, and ideally, the client should correct the confusing source.
Alain Boulé May 9, 2017:
This has nothing to do with networking hardware but with address decoding.

"In partial address decoding, not all address lines in the address bus are used in the decoding process. Figure 127 shows two memory devices configured using partial decoding, where A23 is used to distinguish between the two. In this example, M1 and M2 are repeated 2,048 times through the memory space. When A23=0, M1 is selcted; when A23=1, M2 is selected."

http://users.cecs.anu.edu.au/~Matthew.James/engn3213-2002/no...
Thomas T. Frost May 9, 2017:
Why the bit does matter http://etherealmind.com/basics-what-is-ternary-content-addre... :

"A Ternary CAM (TCAM) stores 0, 1, and “don’t care”. The “Don’t Care” at an additional cost over binary CAM since the internal memory cell must now encode three possible states. This is usually implemented by adding a mask bit (“care” or “don’t care” bit) to every memory cell. An access-list is a common function that uses TCAM (ternary content addressable memory) to have the flexibility to match on various layers of a packets L2-L4 headers. That TCAM memory has the ability to match (0), not match(1) (the binary is counterintuitive there) or not care (wildcard)."
Thomas T. Frost May 9, 2017:
"Don't care" does not mean "negligible" here Some translators here confuse the very specific meaning of this "don't care" bit with "no effect" or "negligible", purely based on a linguistic, but flawed interpretation (at least they provide no technical documentation for their claim that this bit is negligible), apparently without looking up in the many technical descriptions of this bit on the Internet. I have provided links to technical descriptions that clearly explain the meaning and use of this bit. It has nothing to do with unused bits. When we translate technical terms, we need to ensure the technical meaning is preserved. A superficial linguistic translation is not enough.

The link just posted by Alain Boulé is not about this special type of chip with a "don't care" bit at all.
Alain Boulé May 9, 2017:
Address decoding techniques - reference doc Linear Decoding :

In small system hardware for the decoding logic can be eliminated by using only required number of addressing lines (not all). Other lines are simple ignored. This technique is referred as linear decoding or partial decoding. Control signals BHE and Ao are used to enable odd and even memory banks, respectively. Figure shows the addressing of 16K RAM (6264) with linear decoding.

https://www.allsyllabus.com/aj/note/EEE/8086 Microprocessor ...
HERBET Abel May 9, 2017:
Bits négligeables

Proposed translations

+1
10 minutes
Selected

bits "dont' care" (quelconques)

https://fr.wikipedia.org/wiki/Mémoire_adressable_par_contenu
[..]. Cet état additionnel est typiquement implémenté en ajoutant un bit de masque (bit "care" ou "don't care" (quelconque)) à chaque cellule mémoire.
Peer comment(s):
agree Thomas T. Frost : Quelconque seems to be used in French, and "X". And a French IT specialist would understand "don't care" too.
1 heure
agree GILLES MEUNIER
2 heures
disagree Daryo : these are bits on a 16 bit address bus [clue: A0-A12 +"the upper three address bits" = 16 bits], absolutely NOTHING to do with your ref.
4 heures
Whether they are 16 or 32, in a bus or a memory, this has NOTHING to do with their being "don't care" ones. This is a bit state that can be used in a variety of models.
Something went wrong...
4 KudoZ points awarded for this answer. Comment: "Merci"
-1
1 heure
anglais term (edited): don’t care bit

bit quelconque / bit X

This bit is like a joker; it will match anything in a search. "Quelconque" or "X" appears to be the terminology used in French.
Reference:

http://www.techno-science.net/?onglet=glossaire&definition=11665

https://fr.wikipedia.org/wiki/M%C3%A9moire_adressable_par_contenu

Peer comment(s):
disagree Daryo : this is NOT about any kind of "search criteria"
3 heures
Yes it is. You haven't understood what it's about. Read e.g. http://etherealmind.com/basics-what-is-ternary-content-addre... that describes the bit as a "wildcard". Which supporting documentation do YOU have?
Something went wrong...
47 minutes

bits sans effet

Si on veut traduire vraiment ce qui est peut être peine perdue.

--------------------------------------------------
Note added at 3 hrs (2017-05-09 14:29:23 GMT)
--------------------------------------------------

With partial address decoding, some of the address lines which would normally be used to enable the chip select line are left unconnected as far as the address decoding goes; these are called "don't cares". Each line that is specified as a don't care doubles the number of addresses that can select the chip. For example, if A11 was left out of the decoding for the EPROM, it would still respond to address 0x0000 thru 0x07FF, but it would also respond to addresses 0x0800 thru 0x0FFF. So 0x0123 and 0x0923 would address the same internal location.

https://electronics.stackexchange.com/questions/199255/what-...
Peer comment(s):
disagree Thomas T. Frost : That is not the meaning of this bit. It is not without effect. It has the effect of matching anything in a search./No you haven't understood what they are for. They do have effect. Try to look it up in the links in my answer.
46 minutes
Only A12...A0 are used; the upper three address bits are don’t care bits, that is you can set or reset those bits it will be without effect. / Please see the added note in my answer
agree Daryo : exactly that // these address bits [A13 A14 A15] are not needed/not used so their value simply doesn't matter at all. Basics of bare metal programming ...
3 heures
Merci
Something went wrong...
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