Thanks Andrew and Francois! This is a very useful information.
Nimish On Mon, Mar 19, 2012 at 2:36 AM, Francois Kapp <[email protected]>wrote: > I just looked through the attenuator data sheet - there are no settling > time specifications, but I'm sure whatever it is, it will be dominated by > the time taken to set up the registers. > > -Francois > > > On Mon, Mar 19, 2012 at 9:05 AM, Andrew Martens <[email protected]> wrote: > >> Hi Nimish >> >> > To be more specific, we would like to change the attenuation in the >> > KatADC RF front end every 20 ms and we can allow up to 1 ms of dead >> > time/settling time. Do you think this can work? >> >> Just had a quick look through the IIC controller. Seems to need to write >> around 12 words, each 8 bits in size, using a 100kHz clock. This equates >> to around (10us * 12 * 8) ~= 1ms to change attenuation values so 20ms >> should be enough. I am not sure about the settling time of the >> programmable attenuator. >> >> > A related question is how to change this attenuation. I tried using a >> > software register connected to atten* inputs of the KatADC yellow >> > block, but the design would not compile. I have not got time to check >> > at what stage it fails, but I can look into that. I got the design >> > compiled by connecting just the "constant" blocks to these inputs. Is >> > it first of all allowed to have a software register there? If not, >> > what would be the way to change this attenuation dynamically? >> > >> We have software registers that control this value in designs here. If >> software registers work in other parts of your design, they should work >> here - there is nothing special about those ports. You can also set >> these values in software from the PPC if that is easier, the IIC >> controller can be accessed from the PPC. >> >> Regards >> Andrew >> >> >> > > > -- > Francois Kapp > > Sub-system Manager > Digital Back End > meerKAT > > SKA South Africa > Third Floor > The Park > Park Road (off Alexandra Road) > Pinelands > 7405 > Western Cape > South Africa > > Latitude: -33.94329 (South); Longitude: 18.48945 (East). > > (p) +27 (0)21 506 7300 > (p) +27 (0)21 506 7360 (direct) > (f) +27 (0)21 506 7375 > (m) +27 (0)82 787 8407 >
