It is 8x1mux vhdl program main program working with no error, but in test their is some signal i,s,y are shows error and tell i,s,y are already declared. A simple program for 8 x 1 multiplexer is given below. Library ieee;use ieee.std Multiplexers in VHDLCreated on: 2. December 2. 01. 2A multiplexer allows digital signals from several sources to be routed onto a single bus or line.
A 'select' input to the multiplexer allows the source of the signal to be chosen. We look at two multiplexer examples in this tutorial, the first multiplexes two 4- bit input buses to a single 4- bit output bus, the second example multiplexes four single input lines to a single output line. Hooking it up Then, we hook it up. You might wonder why we hooked up the 8-1 MUX as we did. Notice that the first row of MUXes' control bit comes from c 0. The second row of MUXes' control bit comes from c 1. The bottommost MUX's control bit. Using VHDL to Describe Multiplexers Objectives Review Multiplexers Learn CASE Statement within Process. We may use a different statement in the architecture body. Using Selected Signal Assignment Statement We have. Four- Bit Wide 2 to 1 Multiplexer. The 2 to 1 multiplexer is shown below. A logic 1 on the SEL line will connect the 4- bit input bus A to the 4- bit output bus X. A logic 0 on the SEL line will connect input bus B to output bus X. Multiplexer. VHDL Code. The VHDL code for implementing the 4- bit 2 to 1 multiplexer is shown here. If the condition is false, then the signal to the right of the else (B) will be assigned to the output signal instead (this will occur if the signal on SEL is a logic 0). The result of this signal assignment is that a logic 1 on SEL will connect the 4- bit input bus A to the 4- bit output bus X. A logic 0 on SEL will connect the 4- bit input bus B to the output bus X. This video shows the the CPLD with the above code operating. Source Code. The source files for the 4- bit 2 to 1 multiplexer can be downloaded here. The UCF and JED files are configured for use on the home made CPLD board. The VHD, UCF and JED files: mux. The two SEL pins determine which of the four inputs will be connected to the output. SEL will connect A(0) to X, 0. SEL will connect A(1) to X, etc. Multiplexer. VHDL Code. The VHDL code that implements the above multiplexer is shown here. When the logic levels on SEL match one of the values to the right of one of the when statements, the signal to the left of that when statement will be assigned to the output signal (X). The line containing 'others' is required by VHDL to take care of any logic combination that is not taken care of by the preceding statements. This allows for any states besides logic 0 and 1 levels, such as high impedance signals - Z. Note that single signals are assigned logic values by using single quotes, e. A group of signals (vectors) are assigned values between double quotes, e. This is the same when- else as the first example (2 to 1 MUX), but this time multiple when- else constructs are used. The UCF and JED files are configured for use on the home made CPLD board. The VHD, UCF and JED files: mux. VHDL code for 8: 1 Multiplexer. Get the full title to continue reading from where you left off, or restart the preview.
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