help urgent!!! binary to bcd converter

[yein]

I m curently work out this converter but the compilation is not successful. Below is the codes and error message. And I am using shift add3 algorithm for this.

LIBRARY ieee;
USE ieee.STD_LOGIC_1164.all;
USE ieee.STD_LOGIC_ARITH.all;
USE ieee.STD_LOGIC_UNSIGNED.all;

ENTITY projectTest3 IS
port( D : in std_logic_vector(15 downto 0);
Q : out std_logic_vector(15 downto 0));
END projectTest3;
ARCHITECTURE behavioral OF projectTest3 IS
Begin
PROCESS(D)
variable r: STD_LOGIC_VECTOR (15 DOWNTO 0);
BEGIN
r:=(others=>'0');
r(4 DOWNTO 0):=D(15 DOWNTO 11);
FOR i IN 0 TO 9 loop
IF D(10-i)='1' then
r(5+i DOWNTO 0) := r(4+i DOWNTO 0) & '1';
ELSE
r(4+(i+1) DOWNTO 0) := r(4+i DOWNTO 0) & '0';
END IF;

IF r(3 DOWNTO 0) >= 5 then
r(3 DOWNTO 0) := r(3 DOWNTO 0) + "0011";
IF r(7 DOWNTO 4) >= 5 then
r(7 DOWNTO 4) := r(7 DOWNTO 4) + "0011";
IF r(11 DOWNTO 8) >= 5 then
r(11 DOWNTO 8) := r(11 DOWNTO 8) + "0011";
END IF;
END IF;
END IF;
END LOOP;
Q(15 downto 0) <= r(15 downto 0);
END PROCESS;
end behavioral;


Error: a deferred constant declaration without a full declaration is not supported
ANYone can help?
THANKs in advance

 

[bonami172]

Hi,
I think you have recently used the VHDL. Remember that VHDL is the language to design the hardware but not the software. Your program seems to be used for C language in computer. I think the trouble is here :
FOR i IN 0 TO 9 loop
IF D(10-i)='1' then
r(5+i DOWNTO 0) := r(4+i DOWNTO 0) & '1';
ELSE
r(4+(i+1) DOWNTO 0) := r(4+i DOWNTO 0) & '0';
END IF

The compiler cannot generate the hardware to do this. So tell me what your program need to do in detail. I will give you some suggestion.

 

[yein]

Yes. I'm new to VHDL. Actually i am designing a calculator tht can perform addition, subtraction and multiplication only. User will key in the maximum 2 BCD numbers (56+72, 56*4,...).For addition and subtraction, i can do it in BCD. But for multiplication, I have to convert bcd into binary code then the binary result has to convert it back into bcd. I have stucked in the binary to bcd conversion. Hope u can help me... Thanks in advance.

 

[bonami172]

Hi,
You can see more informations in this link :

http://www.tek-tips.com/viewthread.cfm?qid=840645

Or you can search in google with keyword "bcd to binary vhdl".
There are many examples or source code for reference.
Good luck.