from Multisim VHDL Code - Part 1
Design address is changing and one trend is to use embedded devices such as FPGA . These devices internally contain millions of gates reconfigurable programmable logic. We can take a logical function, eg X = AB + CD , and download the FPGA chip, the FPGA internally 'burn' the routes needed to create such a function ng. The main advantage of this lies in the fact that the logic function is hardware, which offers greater reliability in a system.
to program FPGAs using a hardware description language or HDL, the most by using VHDL. This language is text based so it is necessary to know the syntax of it. To learn more VHDL code I recommend a tutorial blog to Help Electronics only gives click here.
In Multisim 11 (and later) versions Student Educational and there is a new feature called Schematic PLD (Programmable Logic Device), and the idea is to create a logic circuit using gates, flip flops, buffers, etc.. and then automatically create the VHDL code necessary to program a FPGA chip. This save much design time.
I note that the PLD of Multisim Schematic was designed in such a way that works hand in hand with a card from National Instruments called Digital Electronics NI FPGA Board . This card is great for pr acetic digital electronics and chip contains a Xilinx Spartan-3E FPGA, as well as peripherals such as LEDs, switches, etc. This card connects via USB to the PC and once generated VHDL code Multisim is ready we can download the FPGA chip on the card.
other chips can be programmed FPGA that are 32 bits and supported by the Xilinx ISE software, this requires a little more work. If you are interested let me know to refer to more resources.
An example of the use of PLD in Multisim Schematic. Our goal will be to perform the function X = AB + CD , so we need four inputs (A, B, C and D) and output (X), as shown in Figure following:
Multisim We will open and select File >> New >> PLD Design ...
Multisim In this first step asks us if we will use the digital card that I mentioned earlier, a new configuration file, or just an empty project. I will select the first option and click the Next :
The name of my design is Logic Function and the FPGA chip used by the digital card is NI XC3S500E. We click Next :
In the previous window we can see the list of input / outputs available on the digital card from NI. I'll select the switches SW0 , SW1, SW2 and SW3 entries corresponding to A , B , C and D my logic function, and for output X will use the LED0 . We
click Finish , Multisim create a blank layout and placement of inputs and outputs selected in the workspace:
The following is to capture our logic circuit, but we'll leave for the next part of the tutorial.
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Greetings!
Fernando
