1. 1/8/2007 - L11 Project Step 5Copyright 2006 - Joanne DeGroat, ECE, OSU1 Project Step 5 Step 2 in behavioral modeling. Use of procedures.

2. 1/8/2007 - L11 Project Step 5 Copyright 2006 - Joanne DeGroat, ECE, OSU2 The nature of the process  Will still use P, K, and R to control the operation.  Previously have use Pctl to compute Pint, Kctl to compute Ki, and then Rctl to generate the final result.  Now will use a combined P&K&R to choose the operation being performed For op A have P,K,R of 1100,1111,1100 For op A AND B have 1000,1111,1100 For op A + B have 0110,0001,0110

3. 1/8/2007 - L11 Project Step 5 Copyright 2006 - Joanne DeGroat, ECE, OSU3 continued  Then we can use a case statement on a variable that concatenates P&K&R to choose which operation to perform. opersw := P & K & R; --Note use of variable CASE opersw IS WHEN “110011111100” => Zout <= A; Cout <= ‘0’; --op A WHEN “001111000110” => neg(A,Ztemp,CoutTemp); Zout <= Ztemp; Cout<= CoutTemp; -- Ztemp and CoutTemp are variables WHEN …

4. 1/8/2007 - L11 Project Step 5 Copyright 2006 - Joanne DeGroat, ECE, OSU4 Note on operations  For logical operation can do vector operations Zout <= A AND B; Where A and B are the input bit vectors And the vectors must be of the same size for a bit-wise vector operation  Arithmetic operations will need procedures One for Add One for 2’s complement One for Subtract that can be an implementation of binary subtraction, or subtraction using 2’s complement addition

5. 1/8/2007 - L11 Project Step 5 Copyright 2006 - Joanne DeGroat, ECE, OSU5 The procedures  The procedures are to be declared in the declarative region of the process  In the declarative region of the process can only declare a procedure body. And thus no procedure declaration part is done.  Scope of procedure is limited to just this process. (We will later move these to a package and write the procedure declaration.)

6. 1/8/2007 - L11 Project Step 5 Copyright 2006 - Joanne DeGroat, ECE, OSU6 Addition  Procedure BINADD A procedure for binary addition using sequential statements. Will make the arguments to the procedure unconstrained so that it will be capable of adding words of any length (constraint that both inputs are the same index range). (right now size is 8 bits, later will use the procedure for 16 bit arguments).

7. 1/8/2007 - L11 Project Step 5 Copyright 2006 - Joanne DeGroat, ECE, OSU7 Unconstrained declaration PROCEDURE binadd (l,r : IN BIT_VECTOR; cin : IN BIT; sum : OUT BIT_VECTOR; cout : OUT BIT) IS VARIABLE carry : BIT; --internal variable carry BEGIN carry := cin; FOR i IN l’reverse_range LOOP -- compute sum for position I, sum(i) := … -- compute carry out for position I into carry variable, carry := … END LOOP; -- assign cout from final value of carry - - I provide a lot but you must finish this

8. 1/8/2007 - L11 Project Step 5 Copyright 2006 - Joanne DeGroat, ECE, OSU8 Highlights on the code  Inputs are “unconstrained” – they can be any size  We will later use these same procedures in a package and the data size will be 16 bits.  Outputs of the procedure are variables. These need to be assigned to the appropriate signal.  Need to use attribute for loop parameter as shown If L declared (x downto 0) such that leftmost bit is the msb and highest index and are progressing 0 to x. THEN L’REVERSE_RANGE has the designation 0 to x

9. Now use the procedure in the case  Within the main process BEGIN … CASE opersw IS WHEN “110011111100” => Zout <= A; Cout <= ‘0’; --op A WHEN “0110xxxxxxxx” => --and add binaddd(a,b,cin,sum,vcout); zout <= sum; cout<= vcout; WHEN “xxxxxxxxxxxx” => … 1/8/2007 - L11 Project Step 5 Copyright 2006 - Joanne DeGroat, ECE, OSU9

10. 1/8/2007 - L11 Project Step 5 Copyright 2006 - Joanne DeGroat, ECE, OSU10 Overall look of code – where things go  Same ENTITY as before ARCHITECTURE v_3 OF adder_8 IS BEGIN  --A single process as just described  PROCESS (sensitivity list) **** PROCEDURES are declared here **** Local Variables  BEGIN opersw:= CASE opersw…….  END PROCESS; END v_3;