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From: "Vinzent Hoefler" <0439279208b62c95f1880bf0f8776eeb@t-domaingrabbing.de>
Newsgroups: comp.lang.ada
Subject: Re: How do I write directly to a memory address?
Date: Tue, 08 Feb 2011 22:46:26 +0100
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Date: 2011-02-08T22:46:26+01:00
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Hyman Rosen wrote:

> I think that's why I'll stick with (byte & (1 << (3 - 1))).
> Or rather, I would most likely write a macro,
>      #define TEST_BIT(n, b) ((n) & (1 << ((b) - 1)))

And it's still wrong. As we all know, C programmers start counting
with zero (including bit numbers), so you're bit-addressing is off
by one.

Assembler can be so much more expressive:

; group A is port B and port C[7:4], definitions are MUTEX
%ASSIGN MODE_A_0 (00b << 5)     ; mode 0 for group A (bits [5:6])
%ASSIGN MODE_A_1 (01b << 5)     ; mode 1 for group A
%ASSIGN MODE_A_2 (10b << 5)     ; mode 2 for group A

; group B is port A and port C[3:0], definitions are MUTEX
%ASSIGN MODE_B_0 (0b << 2)      ; mode 0 for group B (bit 2)
%ASSIGN MODE_B_1 (1b << 2)      ; mode 1 for group B

At least it actually /has/ binary numbers.


Vinzent.

-- 
You know, we're sitting on four million pounds of fuel, one nuclear weapon,
and a thing that has 270,000 moving parts built by the lowest bidder.
Makes you feel good, doesn't it?
   --  Rockhound, "Armageddon"