Why do we use 'j' to represent active LOW signals?

C

Cuthbert

Guest
Hi folks,

I am a beginner of verilog language.
During referring our source code, I saw some active LOW signals
with suffix 'j'. The 'j' means active LOW the same as prefix 'n'. I
am wondering why do we use 'j' to represent active LOW signals? Is
there anyone who can tell me? Thanks.

Cuthbert
 
On Fri, 05 Jun 2009 20:23:23 -0700, Cuthbert wrote:

Hi folks,

I am a beginner of verilog language.
During referring our source code, I saw some active LOW signals
with suffix 'j'. The 'j' means active LOW the same as prefix 'n'. I am
wondering why do we use 'j' to represent active LOW signals? Is there
anyone who can tell me? Thanks.

Cuthbert
Click to expand...
That's not standard, active low signals usually have a _l postfix,
sometimes _n, but never _j.
 
On Sun, 07 Jun 2009 04:54:25 +0000, General Schvantzkoph wrote:

On Fri, 05 Jun 2009 20:23:23 -0700, Cuthbert wrote:

Hi folks,

I am a beginner of verilog language.
During referring our source code, I saw some active LOW signals
with suffix 'j'. The 'j' means active LOW the same as prefix 'n'. I am
wondering why do we use 'j' to represent active LOW signals? Is there
anyone who can tell me? Thanks.

Cuthbert

That's not standard, active low signals usually have a _l postfix,
sometimes _n, but never _j.
Click to expand...
Sometimes _b as well, although I've never understood the etymology.

Regards,
Allan
 
On Jun 7, 2:48 am, Allan Herriman <allanherri...@hotmail.com> wrote:
On Sun, 07 Jun 2009 04:54:25 +0000, General Schvantzkoph wrote:
On Fri, 05 Jun 2009 20:23:23 -0700, Cuthbert wrote:

Hi folks,

    I am a beginner of verilog language.
    During referring our source code, I saw some active LOW signals
with suffix 'j'.  The 'j' means active LOW the same as prefix 'n'. I am
wondering why do we use 'j' to represent active LOW signals? Is there
anyone who can tell me? Thanks.

Cuthbert

That's not standard, active low signals usually have a _l postfix,
sometimes _n, but never _j.

Sometimes _b as well, although I've never understood the etymology.

Regards,
Allan
Click to expand...
The _b is short for "bar". In hand-drawn diagrams (or when the EDA
tool supports it), the negation of A would be written with an overbar
(and pronounced A-bar).
--
Poojan
http://www.circuitdesign.info/blog
 
The _b is short for "bar". In hand-drawn diagrams (or when the EDA tool
supports it), the negation of A would be written with an overbar (and
pronounced A-bar).
Click to expand...
The better example is foobar. The reason that the WWII expression FUBAR
survives in the computer world, and no where else is because in early
computers it was an in joke to call a signal foo and then write the low
true version as

---
foo

which was pronounced foobar. The names foo, bar and foobar crossed over
to the software world where they are still commonly used as generic names
for everything. The overbar disappeared in the early 80s when hand draw
schematics were replaced first by computer generated schematics and then
by Verilog. I've never seen anyone use _b but it makes sense as a tribute
to the old way of doing things.
 
On 7 Jun 2009 19:01:14 GMT, General Schvantzkoph
<schvantzkoph@yahoo.com> wrote:

The _b is short for "bar". In hand-drawn diagrams (or when the EDA tool
supports it), the negation of A would be written with an overbar (and
pronounced A-bar).

The better example is foobar.
Click to expand...
"bar" to mean "not" has been widely (ab)used. In the 80s there
was a semiconductor distributor in the UK whose American franchises
refused to let them sell Japanese silicon. So they set up a
subsidiary company called AMBAR - American-bar - to sell any
non-US manufactured devices.

I've seen _b as an active-low indication in a few companies'
coding standards. I mightily dislike it. If you want to
specify an active-low signal, for heavens' sake say "not"
in front of its name: notReset - or something like that.
Cryptic abbreviations serve no purpose except to create
an internal priesthood. Another possibility, particularly
useful for mode-control signals, is something like
load0_count1
(for a signal that means "do a load operation" when zero,
and "do a count" when 1).

Explicit good. Obfuscated bad.
--
Jonathan Bromley, Consultant

DOULOS - Developing Design Know-how
VHDL * Verilog * SystemC * e * Perl * Tcl/Tk * Project Services

Doulos Ltd., 22 Market Place, Ringwood, BH24 1AW, UK
jonathan.bromley@MYCOMPANY.com
http://www.MYCOMPANY.com

The contents of this message may contain personal views which
are not the views of Doulos Ltd., unless specifically stated.
 
Actually, the military acronym was FUBAR ("Fouled Up Beyond All
Recognition" is the polite version), pronounced like foobar.

I thought foo was just the next generic variable, after fee and fii,
but foobar often has the meaning of fubar (i.e. an error indicator).

I have seen an old vhdl port naming standard that used _b as active
low output, and _j as active low input, _i as an active high input,
and _q as active high output (since all port outputs were supposed to
be registered anyway). I don't know whether 'j' came from j-k flip-
flops, or from just being adjacent to _i.

Andy
 
Andy <jonesandy@comcast.net> wrote:
< Actually, the military acronym was FUBAR ("Fouled Up Beyond All
< Recognition" is the polite version), pronounced like foobar.

< I thought foo was just the next generic variable, after fee and fii,
< but foobar often has the meaning of fubar (i.e. an error indicator).

I was programming many years before I first used a DEC based system.
The manuals commonly used foo.bar for a file name, though it was
sometime later when I found out why.

I have never seen it in IBM systems or documentation.

-- glen
 
On Jun 7, 3:51 pm, Jonathan Bromley <jonathan.brom...@MYCOMPANY.com>
wrote:
On 7 Jun 2009 19:01:14 GMT, General Schvantzkoph

schvantzk...@yahoo.com> wrote:

The _b is short for "bar". In hand-drawn diagrams (or when the EDA tool
supports it), the negation of A would be written with an overbar (and
pronounced A-bar).

The better example is foobar.

"bar" to mean "not" has been widely (ab)used.  In the 80s there
was a semiconductor distributor in the UK whose American franchises
refused to let them sell Japanese silicon.  So they set up a
subsidiary company called AMBAR - American-bar - to sell any
non-US manufactured devices.

I've seen _b as an active-low indication in a few companies'
coding standards.  I mightily dislike it.  If you want to
specify an active-low signal, for heavens' sake say "not"
in front of its name: notReset - or something like that.
Cryptic abbreviations serve no purpose except to create
an internal priesthood.  Another possibility, particularly
useful for mode-control signals, is something like
  load0_count1
(for a signal that means "do a load operation" when zero,
and "do a count" when 1).

Explicit good. Obfuscated bad.
--
Jonathan Bromley, Consultant

DOULOS - Developing Design Know-how
VHDL * Verilog * SystemC * e * Perl * Tcl/Tk * Project Services

Doulos Ltd., 22 Market Place, Ringwood, BH24 1AW, UK
jonathan.brom...@MYCOMPANY.comhttp://www.MYCOMPANY.com

The contents of this message may contain personal views which
are not the views of Doulos Ltd., unless specifically stated.
Click to expand...
Personally I like the suffix better, since I often go through
sorted lists of signals and like to see related signals together.
So if your differential outputs are outa_p and outa_n you
get them next to eachother. Viewdraw schematics allow you to
use the overbar for schematic signals, but the text signal
name in the resultant netlist has a tilde character prepended
like ~foo. Because of this "feature" screwing up my sorted
signal list I now use signals names like FOO_N on the schematic
even though I could use the overbar. If you prefer to use
the entire word "not" you could write FOO_NOT or to
paraphrase Saturday Night Live lingo, FOO
.. . . NOT!

:)

PS - in reference to the OP, I have never seen _j used for
inverted signals. Perhaps it relates to a language other
that English?

Gabor
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top