About AD9862 latching data

Dear everyone:
You see in the FPGA codec datas are interpolated into 32Msps and
sended to AD9862. Then AD9862 interpolates the datas by 4. But AD9862 is
configured to latch datas using CLKOUT1,and CLKOUT1 is 64M. Though
CLKOUT1 is not linked to FPGA, it seems a little confilcting.
So can anyone tell me the how exactly AD9862 latches datas?
Besides,does the 64Msps A/D and 128Msps D/A in the datasheet of AD9862
mean the maximum achievable rates or the fixed working rates? If I
change the VCTCXO,for example 40M,then will AD9862 work according to
40M?
Any answers will be very appreciated.

2012/3/26 signalswdm [email protected]

Dear everyone:
You see in the FPGA codec datas are interpolated into 32Msps and sended
to AD9862. Then AD9862 interpolates the datas by 4. But AD9862 is
configured to latch datas using CLKOUT1,and CLKOUT1 is 64M. Though CLKOUT1
is not linked to FPGA, it seems a little confilcting.
So can anyone tell me the how exactly AD9862 latches datas?
Besides,does the 64Msps A/D and 128Msps D/A in the datasheet of AD9862 mean
the maximum achievable rates or the fixed working rates? If I change the
VCTCXO,for example 40M,then will AD9862 work according to 40M?

The FPGA operates at 64Msps by default, not 32Msps. I agree the clocking
is
a little confusing, we’re not doing true source-synchronous clocking
with
the AD9862. Instead the FPGA and the AD9862 both share the same clock
from
the clock distribution chip, which the AD9862 uses internally as
CLKOUT1.

The AD9862 can work at lower rates. If you are using a B100 or E100, you
can pass the “master_clock_rate” argument to UHD on startup. For
instance,
to clock the AD9862 and FPGA at 32Msps, you can use:

uhd_usrp_probe --args=master_clock_rate=32e6

The D/A rate will be twice the A/D rate; in this example, the D/A
operates
at 64Msps.

–n

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