Re: Alternative Concept

Dmitry Krivoschekov
2007-03-20T15:08:06Z

Amit Kucheria wrote:
> On 3/20/07, David Brownell <david-b@pacbell.net> wrote:
>> On Monday 19 March 2007 7:12 am, Scott E. Preece wrote:
>>> Could you guys present a clear definition of exactly what you mean by
>>> "clock domain" and "power domain"? I can think of several different ways
>>> to interpret the phrases, and I'd like to end up with the same meaning
>>> that you are arguing from...
>> A set of devices that use the same power supply or clock are
>> in the same "power domain" or "clock domain" (respectively).
>>
>> The domains will often be hierarchical, e.g. a base clock
>> rooting other clocks, derived from it by dividers, PLL,
>> or clock gates.
>>
>> Sometimes domains overlap ... e.g. a controller that needs
>> to use one logic level for on-chip logic and another for the
>> external interface; or similarly, different clock rates.
>>
>> Simple chips may not have many domains. Nowadays I think
>> most SOCs have at least a decent selection of clock domains,
>> to eliminate the power drain involved in driving transistors
>> through clock ticks. I understand it's more complicated to
>> have multiple power domains, but the incentive to shrink the
>> leakage current is strong. (So adding on-chip power domains
>> involves tricks to constrain leakage, and not just an ability
>> to operate without a given power rail.)
>
> For the sake of completeness, there is also the Voltage domain. A
> groups of modules supplied by the same regulator would belong to a
> single Voltage domain. Multiple voltage domains allow independent
> scaling of voltages to different domains.
If you forget ability of scaling voltage for the domain, does the domain
become a power domain, IOW is a power domain the simplest case of
voltage domain which doesn't not support voltage scalinig in any of
its states (no scaling in active mode, no scaling in idle mode, no
scaling in
retention mode)?

Thanks,
Dmitry