AMBA AHB

Hi,
  I am designing an AMBA-AHB Master interface.As per the spec ,there
is a delayed version of the HMASTER bus is used to control the write
data mux.So my doubt is ,whether I should have one clk delayed hwdata
from haddr or both can be driven at the same time..It's pretty urgent
to make up the decision...

~~Kumar.

AMBA works in a pipelined manner ... data from a master (HWDATA) should
always be valid one cycle after the address is valid. Data should then be
held
until HREADY is sampled ... when the slave has signalled that it is
complete.

The delayed version of HMASTER is only used in the arbiter for the
AMBA bus.

Mike

"mack" <mmkumar@gmail.com> wrote in message
news:aba94305.0409082246.164990a@posting.google.com...
> Hi,
>   I am designing an AMBA-AHB Master interface.As per the spec ,there
> is a delayed version of the HMASTER bus is used to control the write
> data mux.So my doubt is ,whether I should have one clk delayed hwdata
> from haddr or both can be driven at the same time..It's pretty urgent
> to make up the decision...
>
> ~~Kumar.

mmkumar@gmail.com (mack) wrote in message news:<aba94305.0409082246.164990a@posting.google.com>...
> Hi,
>   I am designing an AMBA-AHB Master interface.As per the spec ,there
> is a delayed version of the HMASTER bus is used to control the write
> data mux.So my doubt is ,whether I should have one clk delayed hwdata
> from haddr or both can be driven at the same time..It's pretty urgent
> to make up the decision...
> 
> ~~Kumar.

By definition, AHB has a separate address phase and data phase that is
to be presented on the bus on two different clocks.  Masters are
responsible for driving those two different phases.  In the case where
there are Muxes controlling what is presented to the rest of the bus,
you can get away with having a master drive both address and wdata on
the same clock.  In this case, the Muxing scheme that is used must
insure that the two phases happen when they are supposed to.  One way
to do this is to generate a delayed version of HMASTER from the
arbiter.  The original HMASTER should be the selector for the address
and control signals and the delayed version should control the mux for
wdata.

See AN 181 for an example of an AHB bus.
http://www.altera.com/literature/an/an181.pdf

Hope this helps.

- Subroto Datta
Altera Corp.

Hi Subroto,
    Thanx for the info.Actually if you are designing only the master
interface for AHB to plug-in to the existing AMBA bus then you are not
very sure that how the internal arbiter is designed(for delayed
HMASTER signal),so can i presume that there will be delayed select
signal for wdata mux and drive both haddr and hwdata on the same clock
or myself should have that addr-data delay??

~~Kumar.
sdatta@altera.com (Subroto Datta) wrote in message news:<ca4d800d.0409091209.3acffdf9@posting.google.com>...
> mmkumar@gmail.com (mack) wrote in message news:<aba94305.0409082246.164990a@posting.google.com>...
> > Hi,
> >   I am designing an AMBA-AHB Master interface.As per the spec ,there
> > is a delayed version of the HMASTER bus is used to control the write
> > data mux.So my doubt is ,whether I should have one clk delayed hwdata
> > from haddr or both can be driven at the same time..It's pretty urgent
> > to make up the decision...
> > 
> > ~~Kumar.
> 
> By definition, AHB has a separate address phase and data phase that is
> to be presented on the bus on two different clocks.  Masters are
> responsible for driving those two different phases.  In the case where
> there are Muxes controlling what is presented to the rest of the bus,
> you can get away with having a master drive both address and wdata on
> the same clock.  In this case, the Muxing scheme that is used must
> insure that the two phases happen when they are supposed to.  One way
> to do this is to generate a delayed version of HMASTER from the
> arbiter.  The original HMASTER should be the selector for the address
> and control signals and the delayed version should control the mux for
> wdata.
> 
> See AN 181 for an example of an AHB bus.
> http://www.altera.com/literature/an/an181.pdf
> 
> Hope this helps.
> 
> - Subroto Datta
> Altera Corp.