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 r0, r0, lsr #23
When reading the ARM programming manual I believe it should.
No, rbit does not allow the "flexible operand" encoding.
But do I gain something ?
If it were possible, at most a few cpu cycles.
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 speeds.
Thomas
Hi Thomas,
My processor flags : -Wpstm32f103rb -Cparmv7m.
The #23 is no typo, I need to reverse 9 bits. I'm using 9 bit
synchronous transmission. My first usart-tests were at 4Mbps. The person
that made the driver recommends max. 6Mbps.
If I need more spare time I'll have to see what DMA can do.
Thanks for all information.
Regards,
Koenraad Lelong.
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