Re: [Discuss-gnuradio] updated packet format on USRP inband signaling

[Eric Blossom]

On Sun, Feb 25, 2007 at 08:53:51PM -0500, Brian Padalino wrote:
> On 2/25/07, Eric Blossom <address@hidden> wrote:
> >That sounds good.  Would you interpret it as a delta-t from the
> >timestamp in the header?  I'm thinking about the case where there are
> >multiple DELAY ops in the payload.
> 
> It would probably be best to interpret it as a delta from the current
> time tick where each operation would be 1 tick.
> 
> If you did it as a delta from the timestamp header, you would have to
> calculate those intermediate deltas - and 32-bit subtractors inside an
> FPGA can run pretty slowly even with the fast carry chains.
> 
> Something like:
>  OP_WRITE_REG
>  OP_DELAY[19]
>  OP_I2C_WRITE
> 
> I could see this showing OP_I2C_WRITE occuring 20 ticks after OP_WRITE_REG.
> 
> What do you think?

I guess I'm concerned that some of the OPS could take more than a
single tick.  E.g., I2C or SPI ops.  Thoses buses run at something
like 100kHz to 400kHz.  If all execution delays are known, then
OP_DELAY seems fine (and easy).

Eric