Re: [f-cpu] Execution unit port

[Yann Guidon <whygee@f-cpu.org>]

hello,

nicO wrote:
> Hello,
> 
> I'm looking for the "usual" definition of the port of a unit :
> 
> 3 data in,
> 2 data out,
"as much as needed"
(ASU could have 4 output ports but this is not yet completely determined).

> SIMD flag,
> clk,
> enable or start,
> reset,
> something for the exception ?
except for the SR unit, no EU needs to report exceptions
(protection violation, but the pipeline is stalled at issue
when the SR EU is used).

FP units can report exceptions if the "IEEE flag" is set
(again : the pipeline is stopped until we are sure that the
result is ok).

concerning the "necessary flags" for example, ROP2 requires the 2 mode
bits and 4 function bits. Some transation and buffering of the 4 function bits
is performed during the Xbar cycle.

> If there is something to say if the outed data is correct or not ?
no. Data are discarded "implicitely" by the Xbar write stage,
by choosing a proper source for the proper register and with the right write mask.

> Does i miss a signal ?
no, except for very special cases, it does the trick.
there's no magic :-)

> nicO
WHYGEE
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