M5221X Bus Frequency

[mjbcswitzerland]

Hi All

I am a little confused as to the maximum bus frequency quoted on the M5221X Product Summary Page:
http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MCF5221X&nodeId=0162468rH3YTLC00M9544...

The M5221X types are given to have 25MHz to 40MHz maximum bus speed.
In the data sheets and user manual the values of 50MHz to 80MHz are specified.

[As a comparison - the M5222X are specified on the product summary page to have max. bus speed of 80MHz, corresponding to the same value of 80MHz as specified in the data sheet].

Is this an error or a different interpretation?

Regards

Mark

www.uTasker.com

[JimDon]

Mark,
Yes, I did notice that. I think the various docs use incorrect terminology. The max. clock rate is 80Mhz, which should be called the System clock, and the (IO) bus clock is system clock/2. So that would mean that the (IO) bus clock is 40 MHz max. At different points they seem to confuse these terms, and possible introduce other terms.  The seem to use "bus clock" to refer to both the CPU (System) bus and the IO bus clock.

[SimonMarsden_de]

Yes, be careful. This problem affects much of the ColdFire documentation.

You need to treat the term 'System Clock' with caution in any ColdFire manual. It is sometimes used for the bus clock and sometimes for the core clock.

In some of the manuals there is a helpful diagram (usually in the PLL section), which shows the clock routing to all the peripherals. You can use it to check which ones receive a divided-by-two bus clock.

[RichTestardi]

Hi Mark,

Isn't the CPU speed twice the (I/O) bus speed?  Or did I misunderstand totally?  All the peripherals seem to operate that way?

-- Rich