umtrx fpga internal clocking

Andrey Sviyazov andreysviyaz at gmail.com
Tue Apr 15 13:23:54 UTC 2014


We'll need stable and quite high sample rate for LTE.
So I'd like PCIe to communicate with embedded PC board or via something
like PCIe fiber optic modules.
But this might require more powerful FPGA.


Best regards,
Andrey Sviyazov.


2014-04-15 14:59 GMT+04:00 sergey kostanbaev <sergey.kostanbaev at gmail.com>:

> Hi guys,
>
> We cannot compare equally B2x0 and UmTRX, since
> - B2x0 has CX3 USB3 interface which has ARM core inside and thus it
> doesn't need a CPU inside FPGA
> - Ethernet handling and USB is quite different, it's hard to have much
> code in common. And SRAM is needed only for Ethernet handling.
> - Also we're taking in mind to support PCIe at some time and PCIe needs
> another handling interface.
> So I don't think we need to move to B2x0 architecture completely.
>
> Probably we can grab some good ideas from B2x0, something like this (but
> I'm not sure that are really good)
>
>
>    - Each DSP module has own reconfigurable vita timer. That's plus.
>    - RX/TX control and  RX/TX framer are new, DSP(DUC, DDC and so on) the
>    same.
>
> What do you think about
>
> Instead of Wishbone bus there used AXI bus.
>
>
>
> On Mon, Apr 14, 2014 at 10:02 PM, Andrew Karpenkov <plddesigner at gmail.com>wrote:
>
>> Hi guys,
>>
>> I took a quick look at B2x0 architecture.
>> And the results is here:
>>
>>    - There is no SRAM and utilization of internal block memory at
>>    Spartan 6 XC6SLX150 is about 70%. So, either we use external memory, or we
>>    need to use a new fpga.
>>    - 2 TRX used about 45% of Spartan 6 XC6SLX150 Slices.
>>    - Instead of Wishbone bus there used AXI bus.
>>    - There is no CPU at all (hard logic).
>>    - I didn't find ICAP module here. But this is  very usefull for a far
>>    away installations.
>>    - Each DSP module has own reconfigurable vita timer. That's plus.
>>    - RX/TX control and  RX/TX framer are new, DSP(DUC, DDC and so on)
>>    the same.
>>    - There is no second signal from GPS module, only uart.
>>    - New serial_to_settings module for a working with devices through
>>    the I2C bus.
>>    - Overall code is very small and look pretty nice.
>>    - All required clock limitations are performed with large reserve.
>>    Input fpga clock is 40 MHz, internal system bus - 100 MHz, DSP clock
>>    frequency is the same with AD9361 DATA_CLK, 64.44MHz.
>>
>>  Please, correct me, if I'm wrong.
>>
>> I think that we need to use B2x0 architecture sooner or later. But this
>> is huge work for a adding SRAM, Ethernet, CPU, ICAP  into FPGA and UHD
>> codes.
>> May be  easier to modify current fpga code than rework B210 code for
>> UmTRX architecture. Don't know..
>>
>> Regards,
>> Andrew Karpenkov
>>
>>
>> 2014-04-09 23:07 GMT+04:00 sergey kostanbaev <sergey.kostanbaev at gmail.com
>> >:
>>
>> I also haven't had a time to look at. Hopefully I'll look at Friday.
>>> On Apr 9, 2014 10:52 PM, "Andrew Karpenkov" <plddesigner at gmail.com>
>>> wrote:
>>>
>>>> Ok. I understand.
>>>>
>>>> I suppose that before make changes in current fpga code, we should make
>>>> a decision exactly which architecture more suitable for UmTRX, N2x0 or B200?
>>>> Sergey, Josh, what do you think about this, pro and con?
>>>>
>>>> Unfortunately, I can look into B200 fpga code only at friday..
>>>>
>>>> Regards,
>>>> Andrew Karpenkov
>>>>
>>>>
>>>> 2014-04-09 20:43 GMT+03:00 Josh Blum <josh at joshknows.com>:
>>>>
>>>>>
>>>>>
>>>>> On 04/09/2014 03:17 AM, Andrew Karpenkov wrote:
>>>>> > Josh,
>>>>> > I'm glad that I answered on most of yours questions. If you need
>>>>> some more
>>>>> > information, don't hesitate to contact with me.
>>>>> >
>>>>> > 104MHz fifo bus in -> cross clock fifo to 26 MHz -> vita tx deframer
>>>>> ->
>>>>> >> paced tx dsp -> out to dac
>>>>> >> in from adc -> paced rx dsp -> vita rx deframer -> cross clock fifo
>>>>> to
>>>>> >> 104 MHz -> 104 MHz fifo bus out
>>>>> >
>>>>> >
>>>>> > According to your idea. I think that this is fine, but are you're
>>>>> sure that
>>>>> > 26MHz is enough for DSP calculations? In N2x0 DSP clock frequency
>>>>> was twice
>>>>> > higher than CPU clock.
>>>>> >
>>>>>
>>>>> Well technically, the DSP only needs to run as fast as the ADC/DAC
>>>>> sample rate. In the current UMTRX design, the DSP calculations
>>>>> themselves are running at 13 MHz. I'm only suggesting moving the VITA
>>>>> framer/deframer into the same clock domain as the DSP units (26MHz).
>>>>> The
>>>>> actual buffering, packet routing, fifo muxing, that sort of stuff will
>>>>> stay in the 104MHz clock domain (it has to be faster because of
>>>>> buffering/sending ethernet packets). And the CPU/ZPU/wishbone clock is
>>>>> independent, and really only for low speed communications -- I would
>>>>> simply keep this at 52 Mhz, but in fact, its clock rate isnt really
>>>>> critical.
>>>>>
>>>>> -josh
>>>>>
>>>>
>>>>
>>
>
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