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首页 > 解决方案 > uvm_sqr_if_base::peek() 和 uvm_sqr_if_base::get_next_item() 有什么区别？

system-verilog - uvm_sqr_if_base::peek() 和 uvm_sqr_if_base::get_next_item() 有什么区别？

问题描述

在 System Verilog UVM 中，TLM 端口中用于序列和驱动程序之间通信的接口 ( uvm_sqr_if_base) 提供了灵活性。对于拉取请求，我将总结此表中的四个选项：

                  blocking   item_done
get_next_item()      yes        no
try_next_item()       no        no
          get()      yes       yes
         peek()      yes        no

...其中阻塞表示如果您调用该方法，但没有准备好提供数据的序列，则该任务将阻塞并等待，直到数据准备好并且可以并且将被返回。

... 其中item_done表示该方法item_done()在成功从序列中拉出项目后也会调用。

peek()和get_next_item()then有什么区别？

考虑来自两个虚构驱动程序的这两个代码片段......

  while(1) begin: loop1                          while(1) begin: loop2
    seq_item_port.get_next_item(req);              seq_item_port.peek(req);
    process(req);                                  process(req);
    seq_item_port.item_done();                     seq_item_port.item_done();
  end: loop1                                     end: loop2

有什么不同？为什么有两种方法可以完成同一件事？它似乎不是 TLM1 与 TLM2 风格。

编辑：

回答下面的问题。在问这个问题之前，我已经查看了源代码。事实上，语言只是略有不同，代码似乎做同样的事情。重点是什么？我错过了什么？

  // Task: get_next_item
  //
  // Retrieves the next available item from a sequence.  The call will block
  // until an item is available.  The following steps occur on this call:
  //
  // 1 - Arbitrate among requesting, unlocked, relevant sequences - choose the
  //     highest priority sequence based on the current sequencer arbitration
  //     mode. If no sequence is available, wait for a requesting unlocked
  //     relevant sequence,  then re-arbitrate.
  // 2 - The chosen sequence will return from wait_for_grant
  // 3 - The chosen sequence <uvm_sequence_base::pre_do> is called
  // 4 - The chosen sequence item is randomized
  // 5 - The chosen sequence <uvm_sequence_base::post_do> is called
  // 6 - Return with a reference to the item
  //
  // Once <get_next_item> is called, <item_done> must be called to indicate the
  // completion of the request to the sequencer.  This will remove the request
  // item from the sequencer FIFO.

对比

  // Task: peek
  //
  // Returns the current request item if one is in the sequencer FIFO.  If no
  // item is in the FIFO, then the call will block until the sequencer has a new
  // request. The following steps will occur if the sequencer FIFO is empty:
  //
  // 1 - Arbitrate among requesting, unlocked, relevant sequences - choose the
  // highest priority sequence based on the current sequencer arbitration mode.
  // If no sequence is available, wait for a requesting unlocked relevant
  // sequence, then re-arbitrate.
  //
  // 2 - The chosen sequence will return from <uvm_sequence_base::wait_for_grant>
  // 3 - The chosen sequence <uvm_sequence_base::pre_do> is called
  // 4 - The chosen sequence item is randomized
  // 5 - The chosen sequence <uvm_sequence_base::post_do> is called
  //
  // Once a request item has been retrieved and is in the sequencer FIFO,
  // subsequent calls to peek will return the same item.  The item will stay in
  // the FIFO until either get or <item_done> is called.

标签： system-veriloguvm

解决方案

Peek绝对来自 TLM1 风格。它使您有机会查看队列中的下一个项目，而无需将其从队列中删除。这意味着您尚未承诺启动该项目。Peeks 可用于两种不同的场景。

  1. 一对多：您可以有多个驱动程序，或单个驱动程序中的多个线程进行窥视，然后决定是否要获取序列项，或忽略该项。让您在peak决定使用get.
  2. 多对一：您可以将多个音序器连接到同一个驱动程序。驱动程序将从其所有连接中查看并决定它想要提交的序列器。

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