verilog程序,ISE 10.1环境下,检查语法和仿真均可,综合出错“ this signal is connected to multiple drivers.”

背景:Xilinx公司的FPGA  ,ISE 10.1 开发环境,  verilog HDL语言

问题描述:检查语法没有错误,用modelsim仿真也可以,但综合时出错,错误如下:

 

ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toSlv> on signal <MeasureFrame<56>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toSlv> on signal <MeasureFrame<48>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toSlv> on signal <MeasureFrame<40>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toSlv> on signal <MeasureFrame<32>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toSlv> on signal <MeasureFrame<24>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toSlv> on signal <MeasureFrame<16>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toSlv> on signal <MeasureFrame<10>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toSlv> on signal <MeasureFrame<0>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toFwd> on signal <MeasureFrame<40>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toFwd> on signal <MeasureFrame<32>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toFwd> on signal <MeasureFrame<24>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toFwd> on signal <MeasureFrame<16>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toFwd> on signal <MeasureFrame<10>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toFwd> on signal <MeasureFrame<0>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toPC> on signal <MeasureFrame<40>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toPC> on signal <MeasureFrame<32>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toPC> on signal <MeasureFrame<24>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toPC> on signal <MeasureFrame<16>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toPC> on signal <MeasureFrame<10>>; this signal is connected to multiple drivers.
ERROR:Xst:528 - Multi-source in Unit <mst_process_format_toPC> on signal <MeasureFrame<0>>; this signal is connected to multiple drivers.

 

此类错误系将某同一个reg变量在多个个always块中进行了赋值操作,此类程序是不可综合的,因此须修改程序。

 

切记,对于同一个reg型变量只能在一个always块中对其值进行修改,当然在其它块中可以引用其值!

 

其实这种错误是可又理解的,试想两个always都在时钟的驱动下工作,如果,我说是如果,在同一个时钟时刻,在两个alway块中对同一reg型赋值条件都满足,那么你让FPGA该怎么做呢?让它听谁哪个always块的呢?

verilog最终是要生成电路在FPGA里面,这让FPGA情何又堪?如何生成电路?


 

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