Re: Burst on 565

Hi,

Memory controller BR and OR registers define behavior
of the EBI for corresponded regions.

SIUMCR defines global EBI behavior and in case
of BURST_EN bit controls burst mode of the EBI, which
is initiated by the EBI upon any external instruction
fetch request from RCPU.

If a BI bit in the memory controller register BRx is
set, the EBI will not expect burst of data, but will
request "emulated" burst by initiating sequence of the
single data bus cycle to fulfill the burst request.

The number of such cycles depends on requesting
address and value of the BRx[BL] bit and can be up to
8.

So to have burst on the external bus following
steps need to be taken:

1) make sure that you external device supports  bursts
and the burst mode is enable - most burstable flashes
require special programming  sequences, which should
not be run from them ..

2) enable burst in the SIUMCR, and in the BRx register
- again the configuration code should not run from
device under configuration.

Note that there is another source of the    burst -
BBC which supports only 4 beat burst and this is
legacy mode, retained from MPC555.

For performace considerations use "SIU" burst and not
BBC burst.

Please, notice that only in revD MPC565 "SIU" burst is
fully functional.


Regards
Alex.
         

--- qty154 <[email protected]> wrote:

> Hello!
> 
> I get quite confused about the burst feature on
> MPC565. There is a 
> burst support in the memory controller, and another
> one in the USIU 
> which can be activated by the SIUMCR[BURST_EN] bit.
> However this bit 
> is not documented among other SIUMCR bits. Moreover,
> it is also said 
> that these two bursts shouldn't be enabled at the
> same time. Would 
> someone please clarify briefly when does USIU burst
> work and when 
> memory controller burst, and how and when to enable
> them?
> 
> I am now reading the latest errata, it is quite a
> breathtaking 
> reading. It is quite unlucky that in the beginning
> of errata several 
> items are listed twice, so to compare it with
> previous errata is time-
> consuming.
> 
> Regards
> Attila
> 
> 
> 
> 
> 
> 
> 
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