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access hub timing — Parallax Forums

access hub timing

innomaninnoman Posts: 5
edited 2008-10-11 22:23 in Propeller 1
hi all,

I wish that cogs 4 achieve hub most faster and regularly possible. somebody could it confirm that if I choose my cogs by separating them from 2, eg 1,3,5,7 that they will once all achieve the hub at least in a minimum of 44 cycles and maximum 47 cycles.

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Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2008-10-11 20:14
    Read pages 24 and 25 of the Propeller Manual. This shows the relationship between the cogs and hub memory access. Any cog can already access hub memory at least once every 22 clock cycles. If your instruction is in a loop, after the first hub access, the cog can be synchronized with the hub cycle (since cogs can be programmed deterministically) and further hub accesses can be as often as once every 16 clock cycles.
  • innomaninnoman Posts: 5
    edited 2008-10-11 20:31
    Sorry but an error seems to be manager introduced into question. it is not about the cog 4 but of 4 cogs. I've read p24 - 25 but a doubt persists, I like to know how much cycles it is needed so that they can all have access to the hub.
    tanks Mike
  • Mike GreenMike Green Posts: 23,101
    edited 2008-10-11 21:01
    The numbers I mentioned are the same whether one cog or all 8 cogs need access to the hub memory. The maximum amount of time is 22 clock cycles. Each cog is assigned a time slot that's two cycles long. A cog can use that time slot for a hub access or it can do something else internally during that time (like execute part of a non-hub instruction).
  • RinksCustomsRinksCustoms Posts: 531
    edited 2008-10-11 22:23
    What mike is saying, is that all cogs DO have access to HUB, just not all at once, all cogs have sequential access to the HUB.

    Post Edited By Moderator (Chris Savage (Parallax)) : 10/13/2008 3:24:00 PM GMT
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