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 blocking 表示如果调用该方法，但没有序列准备好提供数据，则任务将阻塞并等待，直到数据准备好并且可以返回。
... 其中 item_done 表示该方法在成功从序列中拉出一个项目后还会调用 item_done()。
那么 peek() 和 get_next_item() 之间有什么区别？
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
有什么区别？为什么有两种方法可以完成同一件事？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，LANGUAGE 只是略有不同，代码似乎做完全相同的事情。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,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.
解决方法
Peek 绝对来自 TLM1 风格。它使您有机会查看队列中的下一项，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。
- 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执行peeks，然后决定他们是否要获取序列项，或忽略该项目。
peak可让您在决定使用get提交之前查看项目的内容。 - 多对一：您可以将多个音序器连接到同一个驱动程序。驱动程序会查看其所有连接并决定要提交给哪个音序器。