Re: How to indicate a field of bits in a byte

Subject: Re: How to indicate a field of bits in a byte
From: "gschnabl" <gschnabl -at- LivernoisYards -dot- com>
To: "TECHWR-L" <techwr-l -at- lists -dot- techwr-l -dot- com>
Date: Wed, 9 Nov 2005 16:29:25 -0500



----- Original Message -----
From: "Jan Axelson" <jan -at- Lvr -dot- com>
To: "TECHWR-L" <techwr-l -at- lists -dot- techwr-l -dot- com>
Sent: Tuesday, November 08, 2005 10:29 AM
Subject: How to indicate a field of bits in a byte


|
| I sometimes need to describe the usage of bits of data within a byte,
where
| multiple bits in the byte make up a single field.
|
| Example:
|
| Bit 0: End bit
| Bits 1 through 7: CRC bits
|
| Conventions I've seen to indicate "Bits 1 through 7" or similar include
|
| [1:7]
|
| 1..7
|
| 1...7
|
| 1-7, where "-" is an n-dash
|
| or the same but with the most significant bit first, especially when
| followed by data, such as:
|
| [7:1] 1110001
|
| (because the leftmost bit is bit 7).
|
| I'd be interested in any comments/thoughts on which format is clearest, or
| if there's a better format. The audience is engineers/programmers.
|
| (I recently rejoined this list after an absence and am finding it as
| informative as ever.)
|
| Jan Axelson
| www.Lvr.com



Bitfields are not standarized, and the compiler designer or chip-series
manufacturer will choose a means for labeling bits probably out of
tradition, habit, or convention. I'm currently editing 8- and 16-bit
compiler manuals plus two companion assembler manuals. In this area, I just
follow what the compiler engineer uses. Of course, another designer might do
it differently, but not usually after a manual is already in distribution.
So I would ask the lead engineer for what he prefers.

BTW, we use:
[7:1] 1110001
(because the leftmost bit is bit 7


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How to indicate a field of bits in a byte: From: Jan Axelson

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