At the end of the day HDL is just a text-based way of expressing the content of logic schematics. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more.
Asked 8 years, 11 months ago. Active 1 year, 1 month ago. Viewed 38k times. Shashank V M 2, 8 8 silver badges 38 38 bronze badges.
Orange Orange 85 1 1 gold badge 2 2 silver badges 5 5 bronze badges. Add a comment. Active Oldest Votes. Here's how: A process is triggered every time one of the signals on the sensitivity list "clk, reset" in this case changes. So what is going to trigger a state change from waiting to shifting?
Here's the whole code in one chunk: library ieee; use ieee. I sincerely thank you for your help. This makes a lot of sense. All too often am I met with the "multiple driver" error!
This shift register seems to latch in the parallel data and then shift out serially. Very useful for beginners. I really apreciate you. Thank you so much. Its very useful for vhdl beginners. Leave a Reply Cancel reply. Do you have a drawing of your intended circuit? Try to work out your circuit before writing code. By putting your flip-flop instantiations inside a process, you are trying to create flip-flips that somehow magically appear and disappear depending on whether the input SERIAL is high or low.
HW can't do that. An instantiation is not a function call, it is like soldering a chip to a PCB. Experienced VHDL engineers always do that. They might not literally draw the circuit diagram, but as they write their code they know roughly what HW they are expecting.
If they don't know that, they're not doing it properly. Tricky How can I use a for i in to n-1 loop where n is generic when I need to use the iteration variable i as index during the port map? I though it would be done during the synthesis. Since it is clear that I need n Dflipflop or what only changes it the connection between them. Saens If you're doing a port map, then you're doing an instantiation which cannot be done in procedural code, so you will not be using a for loop. That is if you have any conditional statements in your process and your outputs are driven inside these conditional statements then there a high chance that the outputs may never be driven.
To avoid this it is good practice to place a concurrent statement at the beginning of your process to ensure your outputs are being set at least once. This will tell your synthesiser not to create a latch. We are building an 'async transmitter' with fixed parameters: 8 data bits, 2 stop bits, no-parity. To go through the start bit, the 8 data bits, and the stop bits, a state machine seems appropriate.
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