Re: 64B/66B Control Codes Mapping & Bit Order
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.
>
> --
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> Lucent Microelectronics Group - West
> 1381 McCarthy Blvd, Miltpitas, CA 95035
> Work: 408-952-8822 FAX : 408-952-8887 wlee@xxxxxxxxxx
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--
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