Re: Timing differences before / after starting scheduler

[Tim Jaacks <timjaacks@xxxxxx>]

> > Which FIFO? The UART FIFO is 16 bytes, why 8 DWORDs? In the
> > case you mean 8 bytes (half a buffer), 8 bytes in 17 us means
> > 3,75 Mbps. I don't know the LPC2378, but as far as I can see
> > the UART is considered a low-speed interface and is connected
> > to the APB. Maybe you are stretching the hardware a bit?
> >     
>
> I'm guessing it is the SSP serial I/O controller. It has an 8-frame
> FIFO for both RX and TX, and frames are 4-bit to 16-bit.
>
> I'd also guess he is using it as a slave, with messages bigger than
> 8-frames, so has to read from the FIFO fast enough to make space for
> the rest of the message. Using the DMA might be the solution...
>
>     Andrew
>   
It's the FIFO of the SD/MMC interface, which is 16 DWORDs long. I am 
polling for FIFO_HALF_FULL and then read out 8 DWORDs.
I am running the interface with a 9MHz clock, so the data comes in with 
36Mbps. The SD card always sends a complete block of 512 bytes, so I 
have to read the whole block within 114 us.

Before starting the scheduler, all this works perfectly. But as I said, 
after starting the scheduler the reading gets too slow.

What do you mean with I am stretching the hardware?

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