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pull mode vs push mode

onkarkk

 Hi,

Could any help me out in understanding the difference between pull mode and push mode . I am really not understanding this theory . please help me out.

Thanks in advance,

regards,

Krishna Kishore 

Parents
  • hi, The main issue here is when does the sequence driver picks the next "do". In Pull mode, this decision is made right before injecting the item. In Push mode - this decision might be made many cycles before the injection. Consider, for example, the case when the driver picks the next "do" from sequence A. Cycles passes, and in the mean time - seq B proceeds (perhaps it was waiting for some event), and now it grabs the driver. But the driver already picked another "do", not the B's. This results with a scenario not matching user's intention. While developing layered sequences examples (some are included in uvm/uvm_examples), we came to realize several use models when Push mode just wouldn't work (or - more accurate - requires too much user code). Because in layered sequences, there is a delicate synchronization between high layer, low layer, their drivers and BFMs. To your question - we came to conclusion that Pull mode is the recommended mode. We yet have not seen a use model where Push is preferred.
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  • hi, The main issue here is when does the sequence driver picks the next "do". In Pull mode, this decision is made right before injecting the item. In Push mode - this decision might be made many cycles before the injection. Consider, for example, the case when the driver picks the next "do" from sequence A. Cycles passes, and in the mean time - seq B proceeds (perhaps it was waiting for some event), and now it grabs the driver. But the driver already picked another "do", not the B's. This results with a scenario not matching user's intention. While developing layered sequences examples (some are included in uvm/uvm_examples), we came to realize several use models when Push mode just wouldn't work (or - more accurate - requires too much user code). Because in layered sequences, there is a delicate synchronization between high layer, low layer, their drivers and BFMs. To your question - we came to conclusion that Pull mode is the recommended mode. We yet have not seen a use model where Push is preferred.
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