ncsim仿真求助，仿真跑死现象~

sanluht

小弟在运行ncsim原理图仿真时，仿真会在某个时间点停止，不再运行（现象：xxxxns+xxxx，加号前时间停止，加号后依然在跑），是不是某个逻辑冲突了，但是又找不到具体的原因，有没有大侠遇到过这种问题？怎么处理这种问题？请不吝指教！谢谢~~~

majia123qwe

有combinatianal loop，检查一下吧

rivita

检查一下吧

rivita

学习一下

lccchc

回复 2# majia123qwe

你好,能说具体一点吗,我也碰到这个问题了

547925053

回复 5# lccchc


   Combinational loops are among the most common causes of instability and unreliability in digital designs. They should be avoided whenever possible. In a synchronous design, feedback loops should include registers. Combinational loops generally violate synchronous design principles by establishing a direct feedback loop that contains no registers. For example, a combinational loop occurs when the left-hand side of an arithmetic expression also appears on the right-hand side in HDL code. A combinational loop also occurs when you feed back the output of a register to an asynchronous pin of the same register through combinational logic.

ranqi

不错不错不错

thjan65

先改用 modelsim.
修改 modelsim.ini 中的 iteration limit 以確定是不是真的有combination loop-back

zoe0615

logic error. dead lock loop