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Re: Some newbie questions
- To: Andreas Hofer <ho at dsa-ac dot de>
- Subject: [ECOS] Re: Some newbie questions
- From: Richard Panton <rpanton at 3glab dot com>
- Date: Tue, 26 Jun 2001 17:31:25 +0100 (BST)
- cc: ecos discussion list <ecos-discuss at sources dot redhat dot com>
On Tue, 26 Jun 2001, Andreas Hofer wrote:
> We have developed a SA1110 based board used to perform CAN bus
> communication. The CAN controller in use is the Philips SJA1000. Some
> communication partners on the CAN bus expect our board to respond within
> a guaranteed time limit of 40 Microseconds. Guaranteed means hard
> realtime, right? Can eCos meet these requirements?
eCos CAN meet that requirement, but you may have to be careful of how you
use the various DMA channels on the SA1110 (if you use them at all, that
is).
For instance, the LCD controller loads the palette at the beginning of
each frame. This may contain up to 512 bytes, that MAY be loaded in one
DMA burst. Also, the larger the screen resolution, the less cycles are
available for the processor. Finally, it is possible for PC-Card accesses
to take a VERY long time when using the PWAIT feature or when the access
times are set to maximum. So, even at the hardware level, it can be
difficult to have guaranteed response times from the StrongARM.
Richard Panton
3G Lab Ltd.