Related source file is comparators_1.vhd.įound 8-bit comparator greatequal for signal created at line 10. The XST log file reports the type and size of recognized comparators during the macro recognition step: This section contains a VHDL and Verilog description for an unsigned 8-bit greater or equal comparator. The following table shows pin descriptions for an unsigned 8-bit adder with carry.įollowing is the VHDL code for an unsigned 8-bit adder/subtractor. This section contains VHDL and Verilog code for an unsigned 8-bit adder with Carry In and Carry Out. This package contains the unsigned "+" oper ation.įollowing is the Verilog code for an unsigned 8-bit adder with carry out.Įndmodule Unsigned 8-bit Adder with Carry In and Carry Out This package contains the integer to std_logic conversion function, that is, conv_std_logic_vector. In the preceding example, two arithmetic packages are used: Signal tmp: std_logic_vector(8 downto 0) The following table shows pin descriptions for an unsigned 8-bit adder with carryįollowing is the VHDL code for an unsigned 8-bit adder with carry out. Another solution is to convert A and B to integers and then convert the result back to the std_logic vector, specifying the size of the vector equal to 9:.In this case, XST recognizes that this 9-bit adder can be implemented as an 8-bit adder with Carry Out. One solution, for the example, is to adjust the size of operands A and B to 9-bit using concatenation.The reason is that the size of the result for "+" in this package is equal to the size of the longest argument, that is, 8 bit. For example "std_logic_unsigned" does not allow you to write "+" in the following form to obtain Carry Out: If you use VHDL, then before writing a "+" operation with Carry Out, please examine the arithmetic package you are going to use.
This section contains VHDL and Verilog descriptions of an unsigned 8-bit adder with Carry Out. Port(A,B : in std_logic_vector(7 downto 0) įollowing is the Verilog code for an unsigned 8-bit adder with carry in.Įndmodule Unsigned 8-bit Adder with Carry Out Following is the VHDL code for an unsigned 8-bit adder with carry in.
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