how to choose clock frequency for nios components

[Altera_Forum]

Dear All, 

I'm here to ask for a fundamental. When I add a component in a NIOS system often have doubts about the right clock to connect to. I mean, there are some modules that provide outputs to drive external device(jtag uart, lcd, epcs devices....etc). Devices requires correct timing at least in terms of maximum switching speed. I understand that is not realistic to have always all the components in the system clocked with the same clock, so for example clock crossing bridges are povided. But I wuold like to know wich is the correct clock frequency for modules. I mean, where to find the informations about clock selection for jtag uart or epcs controller?  Thanks a lot in advance.

[Altera_Forum]

Hi, 

It depends on the components to use. It's always simpler to have all of them on the same clock, unless you're obliged to do otherwise:  - need pll clock compensation for different parts of a big design.  - have camera or VGA or other that already have a different clock.  - need different performance and power savings strategies on different components that's as far as I know, and I guess the list can be completed...

[Altera_Forum]

thank WASS, 

I was actually asking information on how to find informations about NIOS components clock requirments.

[Altera_Forum]

Did you took a look at the Embedded Peripherals IP user guide : 

http://www.altera.com/literature/ug/ug_embedded_ip.pdf You'll find details for every peripheral, you can "ctl+f" the word "clock", or fully read the peripheral you're interested in.

[Altera_Forum]

:) but not the clock details... 

let's do the case of the Optrex16207 LCD controller core. I don't see any reference to the component clock selection.