[fpc-devel] BBB / PRUS / M3 and fpc

Michael Schnell mschnell at lumino.de
Tue Dec 3 10:51:24 CET 2013

To whomever is interested:

On 07/05/2013 02:11 PM, Michael Schnell wrote:
> Reading the AM3359 Docu (this is the BBB's chip) it has an "Arm Cortex 
> M3 Subsystem" (other then the predecessor AM17xxx that had a PRUS with 
> a TI propriety CPU design). So it seems to be "a standard Cortex-M3 
> core".
I finally found out the truth.

While it is correct that
  - the 335x chip has a coprocessor system called "PRUS"
  - the "PRUS v2" is greatly upgraded vs the AM17xxx "PRUS v1"
  - a coprocessor in the 335x system is a Cortex M3

it is not true that the PRUS processor is a Cortex M3.

In fact it is a dedicated, propriety architecture by TI and can only be 
programmed in ASM. It is very similar to the AM17xxx PRUS but has more 
RAM and more closely coupled peripherals.

But the chip features yet another coprocessor which really is a Cortex 
M3. Same is used for power management.

I have no idea why you would use a 32 Bit processor just for power 
management, but seemingly the on-chip hardware of a Cortex M3 costs 
close to nothing and consumes close to zero power.


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