Problem with integer variable and vector range

[Altera_Forum]

My code: 

 Int is an Integer Variable OutputNumber is a Std_logic_Vector Input   Int <= conv_integer(OutputNumber); MyVector(37 downto (38-Int)) <= Temp(37 downto (38-Int));  Quartus Compiler Error: Error (10454): VHDL syntax error: right bound of range must be a constant   PLEASE HELP ME.

[Altera_Forum]

The VHDL standard does not allow the right-hand side of downto expresions to contain a variable. 

Just use a constant instead of a Int Integer variable.

[Altera_Forum]

Thanks for reply, but i don't know the value of Int. I must convert the "OutputNumber" input to know the value of Int.

[Altera_Forum]

From your code snippet, it's not fully clear, what you want to achieve. If you want to copy a variable number of bits depending on another condition, you can use a for loop iteration scheme. 

for i in 0 to 37 loop if i >= 38 - int then MyVector(i) <= Temp(i); end if; end loop;

[Altera_Forum]

Hello, 

 "OutputNumber" is a Std_logic_Vector(5 downto 0). It is a vector that store the number of output (eg.: "000000" means no outputs; "01010" means 10 outputs and so on....)  The integer variable "Int" store the equivalent integer value: No outputs: Int:=0; 10 outputs: Int:=10 and so on.....  "Temp" is a 38bit vector, but i need to copy only a range to "MyVector"  Int <= conv_integer(OutputNumber); MyVector(37 downto (38-Int)) <= Temp(37 downto (38-Int));  Quartus Compiler Error: Error (10454): VHDL syntax error: right bound of range must be a constant

[Altera_Forum]

Amilcar has already explained, that your code isn't valid VHDL. Try as I suggested or use a similar construct according to VHDL syntax rules.

[Altera_Forum]

Ok, so can you help me with an alternative solution?

[Altera_Forum]

FvM already gave you an alternative solution. 

One other solution would be: if (OutputNumber == "000000") then  MyVector(37 downto (38-0)) <= Temp(37 downto (38-0)); <- This is wrong because your code was wrong end if (OutputNumber == "000001") then  MyVector(37 downto (38-1)) <= Temp(37 downto (38-1)); end if (OutputNumber == "000010") then  MyVector(37 downto (38-2)) <= Temp(37 downto (38-2)); end if (OutputNumber == "000011") then  MyVector(37 downto (38-3)) <= Temp(37 downto (38-3)); end if (OutputNumber == "000100") then  MyVector(37 downto (38-4)) <= Temp(37 downto (38-4)); end ... if (OutputNumber == "01010") then  MyVector(37 downto (38-10)) <= Temp(37 downto (38-10)); end  There is no need to use conv_integer. And pleas use numeric_std instead of standard_arith