verilog语法：数组切片

【转载】https://www.thinbug.com/q/41484219

使用数组切片构造。您可以在Array slicing Q&A

找到更详细的说明

bit [7:0] PA, PB;
int loc;

initial begin
  loc = 3;
  PA = PB;                      // Read/Write
  PA[7:4] = 'hA;                // Read/Write of a slice
  PA[loc -:4] = PA[loc+1 +:4];  // Read/Write of a variable slice equivalent to PA[3:0] = PA[7:4];
end

Verilog 2001语法

[M -: N]  // negative offset from bit index M, N bit result 
[M +: N]  // positive offset from bit index M, N bit result