vivado：mixed level sensitive and edge triggered event controls are not supported for synthesis

環境：vivado2018.2

如下主要部分代碼裏的always塊報錯：

[Synth 8-434] mixed level sensitive and edge triggered event controls are not supported for synthesis

always@(posedge clk or rst) begin
	...代碼內容
end

stackoverflow上的解釋大致爲：
Mixed sensitive list of levels and edges is not synthesizable, because a flip-flop cannot be edge-tiggered and level-triggered at the same time. Check this link: Synthesis of always blocks
因爲一個觸發器不能同時是邊緣觸發和電平觸發的，因此不可被綜合

所以最好統一是邊沿觸發，或者直接去掉rst信號

always@(posedge clk or posedge rst) begin
	...代碼內容
end