Re: Question about IMB

I was just about to make a post, but the search feature is a 
wonderful tool!

Anyhow, I'm currently configuring the TPU on my MPC555 (Phytec Dev. 
Board) to do some input capturing.  I got lost in the technical data 
regarding the clocks, specifically:

1. The MPC555 product brief says it (the MPC555) operates at 40MHz.  
Does this mean that the system clock frequency is 40MHz?

2. Depending on the answer to #1, what is the default IMB speed?  I 
say default because I am trying to do all my programming using 
Matlab's Real-Time Workshop, and I don't know how to (hopefully, 
don't need to) change the IMB speed (as it relates to the system 
clock) from Matlab.  I see from your reply below, Randy, that 
IMB "can" run at the system clock frequency, but assuming I am just 
turning the thing on and downloading a Simulink program, what speed 
does it run at?

...from there, the MPC555 Embedded Coder's Resource Configuration 
Block makes the prescaling/scaling of TCR1 easy.

Thanks for the help, I hope I provided enough info.

Regards,
Liam


--- In [email protected], Dees Randy-rsaf30 <randy.dees@f...> 
wrote:
> the IMB can run at the same frequency as the system clock (up to 
the maximum frequency rating of the device which is either 40, 56, 
or 66 MHz).
>  
> the TPU runs on the same frequency as the IMB, but fastest the 
TCR1 clock can run is system frequency divided by 2 - see the EPSCLK 
settings..
>  
> randy
> 
> -----Original Message-----
> From: James Smith [mailto:jasmith@c...] 
> 
> 
> Hi folks,
> 
> I'm trying to figure out how fast the TPU  on the '565 can go, 
which I  
> understand is related to the frequency of the IMB.  In the 
MPC565 "Fact  
> Sheet"  
> (http://e-www.motorola.com/files/microcontrollers/doc/fact_sheet/ 
<http://e-www.motorola.com/files/microcontrollers/doc/fact_sheet/>  
> MPC565FACT.PDF) it states that the TPU operates at half the 
system  
> speed (so at a max of 28MHz if the 565 is running at 56 MHz).  But 
in  
> AN1778  
> (http://www.freescale.com/files/microcontrollers/doc/app_note/ 
<http://www.freescale.com/files/microcontrollers/doc/app_note/>  
> AN1778.pdf) it seems that the IMB (at least on the 555) can be set 
to  
> the full system speed ("Normally, the IMB (intermodule bus) clock 
is  
> half the system clock, but for this example it has to be set to 
full  
> speed at 20 MHz in the initialization script. This was done to 
maintain  
> consistency if the system clock is set to 40 MHz with a default 
half  
> speed bus of 20 MHz. The IMB can be set to 20 MHz whether the 
MPC555 is  
> operating at 20 or 40 MHz.").
> 
> So could I run the IMB (and therefore the TPU) on the 565 at the 
full  
> 56 MHz?  If so, is there anything wrong with doing this?  For 
instance,  
> would it drop edge counts during quadrature decoding or something 
like  
> that?
> 
> 
> 
> [Non-text portions of this message have been removed]





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