help regarding an open source

Discussion in 'VHDL' started by koyel.aphy, Feb 18, 2014.

  1. koyel.aphy

    koyel.aphy Guest


    Can someone tell what top.vhd is doing, which can be found in the list of vhdl codes in the following link

    It appears to me that load always contain some undefined bits as it is undefined initially and rxdata fills only 8 bits (0 to 7) of load and further these 8 bits are transferred to the bits from 8 to 15 so ultimately only 0 to 15 will contain 1s or 0s and the rest will be undefined. If this happens state and data will contain undefined values and then how the code will work?

    koyel.aphy, Feb 18, 2014
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  2. I do not know where you get the idea from that only 8 bits are transferred
    to bits 8 to 15.

    Lines 180 and 181 form a 344 bit shift register, where one byte of data is
    shifted in at a time:

    180: load(343 downto 8) <= load(335 downto 0);
    181: load(7 downto 0) <= rxdata;

    The upper eight bits are shifted out, to lower eight bits receive the data.

    The two lines just as well could have been written as one line:

    load <= load(335 downto 0) & rxdata;

    For the rest of the functionality of top.vhd: no idea, if have not looked
    into it any further.
    Paul Uiterlinden, Feb 18, 2014
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  3. koyel.aphy

    koyel.aphy Guest

    got it.

    Thank you very much! Further information on top.vhd is welcome.

    Best Regards,
    koyel.aphy, Feb 18, 2014
  4. koyel.aphy

    koyel.aphy Guest


    I am unable to understand in top.vhd why the condition rxstrobe =1 is kept while using the condition hit =1 as it may happen that rxstrobe =0 and hit =1 and then the statements under hit =1 will not be executed. It is needed to detect hits and if a hit occurs (hit = 1) and rxstrobe is 0 then the hit will not be detected but it needs to be in bitcoins. Please help if possible.

    koyel.aphy, Feb 19, 2014
  5. koyel.aphy

    koyel.aphy Guest

    one further question is: 'nonce' is being fed to the input in miner.vhd and'hit' is an output, which is obtained as

    hit <= '1' when outerhash(255 downto 224) = x"00000000" and step = "000000" else '0';(taken from miner.vhd)

    'outerhash' depends on the value of 'nonce' somehow but the 'nonce' for which I get the hit (hit means 'hit'=1) is not the one that appears (in 'nonce' signal) when 'hit' hits (gets the value of 1) as 'nonce' keep on incrementing every clock pulse and by the time a 'nonce' gives rise to a hit, thevalue of 'nonce' has incremented and changed to some other value. So in top.vhd under the if condition (if hit ='1') txdata gets the value of that nonce that appears when 'hit' hits but not of that nonce that causes the hit. But in bitcoin mining as far as I understood we need to find the nonce that causes the hit ('hit' gets a value of 1). I am unable to find out whereI am wrong. Please point that out and clarify.

    Many thanks,
    koyel.aphy, Feb 19, 2014
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