On 04-05-12 14:53, Koenraad Lelong wrote:
On 04-05-12 14:31, Thomas Schatzl wrote:
...
Compared to the other variants (e.g. with the multiplies, except for the
table lookup) you already save a lot of cycles - although I guess they
would be sufficiently fast anyway, considering the typical
On 7 May 2012, at 13:26, fpc-pascal-requ...@lists.freepascal.org wrote:
Message: 4
Date: Mon, 07 May 2012 12:59:58 +0200
From: Koenraad Lelong ko...@de-brouwerij.be
Subject: Re: RE : RE : [fpc-pascal] Reversing bit-order of byte
To: fpc-pascal@lists.freepascal.org
Message-ID: 4fa7ab2e
On 03-05-12 13:27, Thomas Schatzl wrote:
...
function reverse(b : byte) : byte; assembler; nostackframe;
asm
rbit r0, r0
// rbit reverses the whole word, so now you have
// your value in bits 31-24... so shift right by that amount
// should fix this up (bits 23-0 contain junk, we
On 03-05-12 13:27, Thomas Schatzl wrote:
...
function reverse(b : byte) : byte; assembler; nostackframe;
asm
.long 0xe6ff0f30 // rbit r0, r0
lsr r0, r0, #23
end;
Hi,
I've been looking a bit further at this.
I disassembled the code and this is the result :
8000150: e6ff0f30
Hi,
On Fri, 2012-05-04 at 14:14 +0200, Koenraad Lelong wrote:
On 03-05-12 13:27, Thomas Schatzl wrote:
...
function reverse(b : byte) : byte; assembler; nostackframe;
asm
.long 0xe6ff0f30 // rbit r0, r0
lsr r0, r0, #23
end;
Hi,
I've been looking a bit further at this.
I
On 04-05-12 14:31, Thomas Schatzl wrote:
It might be good to compile with -Cparmv6 (or -Cparmv7, do not know what
type the processor you use is), this generates a better return
instruction (bx lr) - and for the rbit instruction you need armv6
already.
Wouldn't it be possible to do
rbit
Hi,
I'm porting a driver, originally written in C, for an LCD to be used
with an embedded arm-processor (STM32).
The original driver uses SPI, my driver will use a USART in synchronous
mode because the STM32 has no SPI for 9-bit. Unfortunately, the
bit-order is reversed between SPI and USART
Dne 3.5.2012 9:11 Koenraad Lelong fpas...@brouwerij.homelinux.net
napsal(a):
Does anyone knows an efficient way to reverse bit-order of a byte for the
arm-processor ?
Lookup from a 256 byte precomputed table?
Or I misunderstood the task.
-jan
___
Koenraad Lelong wrote:
Hi,
I'm porting a driver, originally written in C, for an LCD to be used
with an embedded arm-processor (STM32).
The original driver uses SPI, my driver will use a USART in synchronous
mode because the STM32 has no SPI for 9-bit. Unfortunately, the
bit-order is
Hi,
On Thu, 2012-05-03 at 07:55 +, Mark Morgan Lloyd wrote:
Koenraad Lelong wrote:
Hi,
I'm porting a driver, originally written in C, for an LCD to be used
with an embedded arm-processor (STM32).
The original driver uses SPI, my driver will use a USART in synchronous
mode
Hi,
I'm porting a driver, originally written in C, for an LCD to be used
with an embedded arm-processor (STM32).
The original driver uses SPI, my driver will use a USART in
synchronous
mode because the STM32 has no SPI for 9-bit. Unfortunately, the
bit-order is reversed between SPI
If you want to go assembly:
function ReverseBits(const Value: LongWord): LongWord; register; assembler;
asm
BSWAP EAX
MOV EDX, EAX
AND EAX, 0h
SHR EAX, 1
AND EDX, 0h
SHL EDX, 1
OR EAX, EDX
MOV EDX, EAX
On 03-05-12 10:45, Ludo Brands wrote:
You might also look into the RBIT instruction which does this in one cpu
cycle. See
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0489c/Cihjgdi
d.html and applied to the STM32 USART
http://forum.micromouseonline.com/viewtopic.php?f=7t=460
Thanks all for your replies.
I already found the RBIT-instruction. I also found out I need
to study
the arm assembly language ;-)
But how do I get my variable ? Is that in some register ? Is
there any
documentation about such things ? Then I can use inline assembly.
ARM has
Hi,
On Thu, 2012-05-03 at 12:54 +0200, Ludo Brands wrote:
Thanks all for your replies.
I already found the RBIT-instruction. I also found out I need
to study
the arm assembly language ;-)
But how do I get my variable ? Is that in some register ? Is
there any
documentation
On 03.05.2012 10:50, David Butler wrote:
If you want to go assembly:
function ReverseBits(const Value: LongWord): LongWord; register; assembler;
asm
BSWAP EAX
MOV EDX, EAX
AND EAX, 0h
SHR EAX, 1
AND EDX, 0h
SHL EDX,
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