Re: 64B/66B Control Codes Mapping & Bit Order
Ben and Pat,
Your exchange makes me feel old and crusty. 22.2.3.2.1 was written a mere
7 years ago! But that is an eon in internet years, so now it is part of the
"long history" of ethernet standards, having earned its way into the
hallowed scripture.
It's like having one of your kindergarten finger paintings hung in the
Sistine Chapel.
The message to all of you whippersnappers out there is that you should
be very careful about what you write. Someday, it might be treated as
gospel, even if you didn't have a clew when you wrote it. The other
message is that precedent is a wonderful guide, but you don't have
to be a slave to it. Better ideas come along every day, and those who
went before you may have made their decisions on the basis of less
information than you possess today.
Please pass the tapioca and warm milk.
Howard Frazier
DomiNet Systems, Inc.
Ben Brown wrote:
>
> Pat,
>
> Given the long history that you reminded me of, I'll drop my
> request. This bit ordering has always confused me but I agree
> that we probably shouldn't change it.
>
> Ben
>
> pat_thaler@xxxxxxxxxxx wrote:
> >
> > Ben and Wesley,
> >
> > In these drawings, I was consistant with 802.3's usual notational
> > conventions
> > which show bit fields with the LSB/first transmitted bit on the left. For
> > instance,
> > see Figure 3-1. If you search the base standard for LSB, you will find that
> > almost
> > all* figures and binary bit representations (see 22.2.3.2.1 for an example)
> > are
> > shown with least significant bit on the left while hex representations of
> > fields
> > are shown in the normal order. I didn't make it that way but at this point
> > we
> > should not change it.
> >
> > Pat
> >
> > *The only deviant I found was 23-7 but the code tables for 23 (see Annex
> > 23A)
> > follow the convention.
> >
> > -----Original Message-----
> > From: Wesley Lee [mailto:wlee@xxxxxxxxxx]
> > Sent: Monday, October 09, 2000 12:33 PM
> > To: stds-802-3-hssg@xxxxxxxx; bbrown@xxxxxxxx
> > Subject: Re: 64B/66B Control Codes Mapping & Bit Order
> >
> > Ben,
> >
> > I'd support you in recommending to flip the order of bits in Fig 49-5 as
> > you suggest in the following. Table 49-1 shows bits msb->lsb
> > but fig 49-5 shows the opposite so one can't simply stuff the
> > control codes in table 49-1 into fig 49-5.
> >
> > Regards,
> > -Wesley Lee
> >
> > ben brown wrote:
> > [snip]
> > Hope this helps. Although it might be too late to make
> > a dramatic change to this table at this point (simply
> > because people are beginning to be familiar with it),
> > I would be eager to recommend to the clause editor that
> > this table be redrawn where the first column changes the
> > order of the bytes from D0...D7 to D7...D0. Then, move
> > the SYNC column to the far left and reverse the order of
> > those bits (DATA = 10, CONTROL = 01). The Block Payload
> > column could then be re-ordered to show D7...D0 for the
> > Data Block Format and C7...C0, Type Field for Control
> > Block Format. This way, the 66-bit field is laid out
> > in front of you with [65] (the msb) on the left and [0]
> > (the lsb) on the right, the way many of us are most
> > familiar with looking at numbers or fields. Also, the
> > hexadecimal equivalents of fields, which are written with
> > msn (most significant nibble) on the left and lsn on
> > the right, could be simply expanded into their binary
> > equivalents without having to perform a mental bit swap
> > to match the table.
> >
> > --
> > ==================================================================
> > Lucent Microelectronics Group - West
> > 1381 McCarthy Blvd, Miltpitas, CA 95035
> > Work: 408-952-8822 FAX : 408-952-8887 wlee@xxxxxxxxxx
> > ==================================================================
>
> --
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> Benjamin Brown
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