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
> Subject: Re: RE : RE : [fpc-pascal] Reversing bit-order of byte
> To: fpc-pascal@lists.freepascal.org
> Message-
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 uart
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
r
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 fu
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
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 shif
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,
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
> > do
> 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
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=7&t=460
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
> 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
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
>
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 reversed
Dne 3.5.2012 9:11 "Koenraad Lelong"
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
___
fpc-pascal maillist - fpc-pa
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 t
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