![]() ![]() So you will need to think about what signal needs to be of what type and what types of operands the functions you are using require and cast accordingly.- fpga4student. result < vect sll 1 output : vect 1 0 X 1 Z result 0 X 1 Z 0 In SLL LSB bit is filled 0. Shift register with parallel load, serial right and left shift s01 right shifts, s10 left shifts, s11 loads parallel data When gbar00 data lines are. The basic problem you are having is one of type conversions. OUTPUT A(N downto to_integer(unsigned(X))), others => A(N)) WHEN OPERATION = "1001" ELSE I think the proper casts would be something like this (but you'll have to double check me as I don't have a VHDL compiler on this machine): -Declaration Make sure to enable the VHDL-2008 switch. There are different ways to describe shift registers. So you can define your inputs and outputs as BIT_VECTOR instead of STD_LOGIC_VECTOR and then use a cast to get just your X into an integer. 1 In addition to what trumpetlicks said, use these packages instead. The left operand must be a BIT_VECTOR and the right must be an integer. If you want to use sra, then you need to use the correct types. There are a couple of ways to go with this. (A <= X(N) & X(N downto 1)) WHEN OPERATION = "1001" ELSE STD_LOGIC_VECTOR(SIGNED(A) - SIGNED(B)) WHEN OPERATION = "1000" ELSE STD_LOGIC_VECTOR(SIGNED(A) + SIGNED(B)) WHEN OPERATION = "0111" ELSE b) Create a VHDL design entity for a 4-bit shift register which is active on the rising edge of the clock The register should be able to shift left. STD_LOGIC_VECTOR(SIGNED(A) - 1) WHEN OPERATION = "0110" ELSE STD_LOGIC_VECTOR(SIGNED(A) + 1) WHEN OPERATION = "0101" ELSE TEMP_OUTPUT <= (A) WHEN OPERATION = "0000" ELSE Signal TEMP_OUTPUT : STD_LOGIC_VECTOR(N downto 0) OPERATION : in STD_LOGIC_VECTOR(3 downto 0) -Allows us up to 16 operationsĪLU_OUTPUT : out STD_LOGIC_VECTOR(N downto 0)) Uncomment the following library declaration if instantiating ![]() The vacant least significant bit (LSB) is filled with zero and the most significant bit. arithmetic functions with Signed or Unsigned values A Left Logical Shift of one position moves each bit to the left by one. shift left arithmetic(sla), shift right arithmetic(slr), rotate left(rol) & rotate right(ror) 1001010 sll 2 is 0101000 -shift left by. bitsll shifts zeros into the positions of. Uncomment the following library declaration if using c bitsll( a, k ) returns the result of a logical left shift by k bits on input a for fixed-point operations. Instead of filling the LSB of the result with zero, it copies the original LSB into the new LSB. Could anyone point me in the right direction? The VHDL arithmetic left shift operator is unusual. To reiterate, I need to shift left/right A by X bits. This causes Type of OUTPUT is incompatible with type of <= error ![]() OUTPUT <= (A sra X) WHEN OPERATION = "0000" ELSE However the methods I know of shifting left/right, either won't work because the values are defined as STD_LOGIC_VECTOR: -DeclarationĪ, B, X : in STD_LOGIC_VECTOR(N downto 0) I'm attempting to create a parametrizable ALU which handles N-Bit signed data. ![]()
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