Re: If ...
- From: BeamEnds <lrspares45@xxxxxxx>
- Date: Wed, 06 Jun 2007 11:31:02 -0700
On May 16, 9:55 am, "manatba...@xxxxxxxxxxx" <manatba...@xxxxxxxxxxx>
wrote:
On May 15, 11:43 pm, "simon" <s...@xxxxxxxxxx> wrote:
<manatba...@xxxxxxxxxxx> wrote in message
news:1179218778.058940.223380@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On May 14, 11:30 pm, "simon" <s...@xxxxxxxxxx> wrote:
"Steve" <stephen.ma...@xxxxxxxxx> wrote in message
Having so many available allows you to use something close to the
number on the side of the loco which makes it much easier to operate a
layout. How are you going to remember the address for all of your
locos?
See other reply for a much better method.
Hornby elite has 254 - way more than I will need in the next 10 years.
This just shows Hornby's strange design choices. The normal choice,
given the way DCC works, is to limit to standard adressing with up to
127 (limited to 99 "two digit" on some systems) addresses or support
extended addressing up to 9999 (hence "4 digit"). Instead, Hornby give
you a middling dog's breakfast that is neither one, nor the other.
MBQ
Here we have an example of an unfair rubbish claim.
Rubbish!
So how is 254 any
stranger than 127, 99 or 9999. You may notice a relationship between 127 and
254. However how 127 relates to 99 or 9999 i do not know.
If you knew anything about the way DCC works, you would understand the
significance of 127 being the upper limit for normal or "2 digit"
addressing.
255 is hex FF or 1111 1111 in binary. So in digital terms very reasonable
design choice.
But not for DCC. You either use a single byte to store a normal
address or two bytes to store an extended address. Trying to squeeze a
bit of both into one byte is a strange design choice. It says to me
that the designers were so short of memory that there is very little
scope for future enhancements.
MBQ
I think you are confusing binary encoding with Binary Coded Decimal as
used in the very early days of computing (and still in some specific
applications). If DCC standards are using BCD they have made a huge
blunder, as binary addressing can be extended by simply making the
addressing word wider 16-bit, 32 bit, 64 bit etc. - with well designed
software and hardware extending the address range is trivial (indeed 4-
bit address decoders that almost literaly plug together have been
available for years).
Richard
.
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