Re: CRC -16 component

Dear all,
I would like to thank you for all what you have done in this project. It was
interesting to see that some work are going on.

I would like to make some explanations to the NOUR design specifications
document and some comments about your interpretation of the design.

- Since bluetooth works on 1MHz we have to process the system at faster clock
rate specially if we are going to make serial processing to reduce the logic
size. For that reason there is a block that generates pulses at 1 MHz rate
while the system is going to operate at higher clock rate. We can in this way
speed up the operations of other parts  that are not dependant on the
inoput/output stream and use single clock in the system to avoide multple
clocks.

- in the CRC block (and most Data path blocks) I supply two data inputs and
do multiplexing inside the block because I do not want to make external
multiplexors. Besides that this will simplify teh system controller so it can
control only teh blocks not the muxs.


I'll try in the coming days to read the documents and send my comments.

Best regards,
Jamil Khatib

On 3/1/2004, "Mohamed Salem" <[email protected]> wrote:

>Dear All,
>
>This presents a detailed description of the CRC-16 component
>functionality in the bit-stream processing of the bluetooth baseband
>datapath.
>(This will be added to the HW spec. document on NOUR folder on HA site)
>-------------------
>
>Processing description:
>------------
>-The CRC-16 will process the data of the payload (user-data.) in TX and
>CRC-16 part in the received packet in RX direction.
>
>Note: Bluetooth Packet is composed of the following:
>{Header, HEC, Payload, CRC-16 Value on USER-data }
>
>-Some definitions:
>
>Payload : User-data ; pure data coming from the upper bluetooth layers
>and stored in the TX-Buffers (at the Transmitter).
>TX- Buffers : 32 bits width , read from buffer one bit at a time.
>The DPRAM technology is suitable to implement the TX/RX buffers
>according to this context) .. will be revisted later while desiging the
>buffers.
>
>-Main Function:
>-The function of the CRC-16 is to evaluate the CRC-16 value on the
>payload(user-data) and append it to payload (TX)
>Check for the CRC-16 value correctness in the recieved packet and inform
>whether it is passed check or failed(RX)
>
>-The CRC-16 implements the CCITT (X16 + X12 + X5 + 1)
>
>-The CRC-16 uses a 16 bit LFSR register which has particular (Xoring)
>for certain Flipflops outputs that are fedback to another FF inputs of
>the LFSR.Refer to figure 3 in HW specs on the NOUR folder on HA site.
>
>-The  data is flowing to the block in serial fashion each clock cycle of
>1 MHZ of system clock.
>
>-The LFSR is initialized to ZEROS (seed-value) of the LFSR using an
>initialization input signal at the start of the system.
>
>-The system controller will enable the block for operation before the
>start of CRC -16 processing using an "enable" input signal.
>
>-At the end of payload (user-data) the main system controller will
>inform the CRC-16 by asserting a "drain" input signal high.
>
>-The drain signal should be asserted "1" for 16 clock cycles.When
>working on CRC-16 processing the drain signal should be (zero) and the
>output should be maintained to the value of the input data ( a 2-1 MUX
>is used for that purpose )
>
>-The 16 clock cycles are enough to "Drain" the LFSR.Hence, the CRC value
>(16 bits)would be appended to the payload while TX operation.
>
>-In the RX direction, whenever the CRC part is checked and verified the
>content of the LFSR should be "Zeros" .Hence, the CRCMATCH output signal
>should be asserted high , indicating the CRC check correctness.
>
>--- The signal description of the CRC-16 block :
>
>Input signals:
>     txRxClk      : 1 MHz clock.
>     sysReset_n   : Active low global reset signal
>     txRxDataIn   : A multiplexed (txData: at the time of
>                    transmit and rxData: at time of reception)
>                    data on which the block has to
>                    calculate/check CRC-16
>     init         : A pulse to initialize the LFSR of the CRC-16
>                    block ( This signal should be asserted for
>                    at least a clock period of txRxClk before
>                    start of each transaction).
>     drain        : This signal gets asserted in the transmit
>                    direction only, when the data is over and
>                    the calculated CRC-16 has to be appended,
>                    it should be high of 16 clocks of txRxClk in
>                    turn draining all the 16 bits of CRC-16
>                    LFSR.
>     enableBlock  : It enables the LFSR to calculate/check the
>                    CRC-16. (I am not sure whether it is
>                    required or not, but it's better to have it.
>                    if it is not required it will be tied to
>                    "1".)
>
> Output signals:
>
>      txRxDataOut  : If the drain =3D=3D "0"; it holds the value
>                     of txRxDataIn.
>                     If the drain =3D=3D "1"; it holds CRC-16
>                     calculated value.
>       crcMatch    : Whenever the value of the LFSR is equal to
>                     "0", the crcMatch gets asserted. It is
>                     receive controller's duty to sample it at
>                     the end of the packet, to know whether
>                     CRC-16 has passed or not.
>
>Block-Diagram:
>will be added to HW spec document on NOUR folder.
>
>----------------------------------------------------------------------
>The details of the CRC-16 component will be added to the Bit-stream HW
>spec. document. version 0.1
>--------------------------------
>By March 8th , the whole Architecture and explanation of the baseband
>datapath should be available in details on our spec. document which is
>going through the review and update process this week.
>-----
>Waiting for feedback and review ..
>
>Thanks all for your efforts ..
>
>Best Regards,
>
>=09Mohamed A.Salem
>
>
>
>
>--------------------------
>NOUR Mailing List
>Handasa Arabia Organization
>http://www.handasarabia.org
>[email protected]
>
>Message number 114

--------------------------
NOUR Mailing List
Handasa Arabia Organization
http://www.handasarabia.org
[email protected]

Message number 116