Re: [Socketcan-users] Fwd: sja1000 BasicCAN mode

[Oliver Hartkopp <socketcan@hartkopp.net>]

On 17.11.2011 17:11, Kurt Van Dijck wrote:

> On Thu, Nov 17, 2011 at 07:58:09PM +0400, Yuriy Kiselev wrote:
>> 2011/11/15 Heinz-Jürgen Oertel <oe@port.de>
>>
>>>
>>>> -----Original Message-----
>>>> From: socketcan-users-bounces@lists.berlios.de [mailto:socketcan-users-
>>>> bounces@lists.berlios.de] On Behalf Of Kurt Van Dijck
>>>> Sent: Tuesday, November 15, 2011 9:22 AM
>>>> To: Yuriy Kiselev
>>>> Cc: socketcan-users@lists.berlios.de; linux-can@vger.kernel.org
>>>> Subject: Re: [Socketcan-users] sja1000 BasicCAN mode
>>>>
>>>> On Mon, Nov 14, 2011 at 09:08:29PM +0400, Yuriy Kiselev wrote:
>>>>> Hello!
>>>>> Implementation of BasicCAN mode for SJA1000 is in attachment.
>>>>> Now SJA1000_PELICAN_MODE macros in sja1000.h is used for definition
>>>> PeliCAN
>>>>> or BasicCAN mode. It would be nice to create some menuconfig-wrapper, I
>>>>> think.
>>>>> I use this code for a few weeks and it looks stable.
>>>> I see no reason to use BasicCAN mode instead of PeliCAN mode.
>>>> Instead, I do see reasons to use PeliCAN mode:
>>>>
>>>> * no problems when 29bit frames appear on the bus
>>>> * rx queue of 64 byte.
>>>>
>>>> What is your motivation not to use PeliCAN mode?
>>>>
>>>> Kurt
>>>
>>> Kurt is correct. For my understanding, the so-called basic CAN mode of the
>>> SJA1000 is a compatibility mode for the 82c200. It makes no sense to
>>> support it any more with SJA1000 devices.
>>>
>>>  Heinz
>>>
>>
>> Yes, BasicCAN mode is for specific designed devices. My device has only
>> 5-bits address bus and I can't use PeliCAN mode.
> Still, properly attached SJA1000 is better used in PELICAN mode. I'm sure
> you agree.
> 
> But I see your point.
> Must your hardware be supported by SJA1000?
> Or by a completely seperate 82c200 driver?
> You probably can start from the SJA1000.


AFAIK the SJA1000 driver only uses 32 byte of address space - so 5 bit are ok!

Even if the address space of the SJA1000 can be 128 bytes in PeliCAN mode,
these addresses beyond register 31 are usually not in use.
Registers 32 - 127 only contain a view into the internal registers and FIFOs
nobody is using, as the FIFO is also implemented in the standard RX/TX frame
registers.

Please check the SJA1000 spec, page 21/22 (PeliCAN address space layout)

Regards,
Oliver