The comments were getting too long. Consider the following block diagram: This represents an unrolled loop (for i in 0 to 7 loop) and shows that no add +3 occurs before i = 2 for the LS BCD digit and no add +3 occurs before i = 5 for the middle BCD digit, and no … Read more
Constructing a Minimal, Complete, and Verifiable example containing your process: library ieee; use ieee.std_logic_1164.all; entity sequent_exec is end entity; architecture foo of sequent_exec is signal a: std_ulogic := ‘1’; signal b, c: std_ulogic := ‘0’; signal clk: std_ulogic := ‘0’; begin CLOCK: process begin wait for 10 ns; clk <= not clk; if now > … Read more
The effect you are witnessing is called “bouncing” of the switch. You need to “debounce” the external input. How to synchronize an external input An external input is not synchronous to the internal clock domain. Thus signal edges within the setup or hold time of a register could cause metastability. You need to synchronize your … Read more
You have dout and count assigned in both processes. Neither are resolved signals. From IEEE Std 1076-1993: 12.6.1 Drivers Every signal assignment statement in a process statement defines a set of drivers for certain scalar signals. There is a single driver for a given scalar signal S in a process statement, provided that there is … Read more
Use the ieee.numeric_std library, and the appropriate vector type for the numbers you are working on (unsigned or signed). Then the operators are `sla`/`sra` for arithmetic shifts (ie fill with sign bit on right shifts and lsb on left shifts) and `sll`/`srl` for logical shifts (ie fill with ‘0’s). You pass a parameter to the … Read more
Variables get updated as you assign them. Signals get update in the next delta cycle (at the earliest). a := ‘1’; — variable assert a = 1; b <= ‘1’; — signal computationUsing(b); –reads old value of b — new value will be visible after this process ends or some time passes Jan Decaluwe explains … Read more
Your code seems very mixed up. There is a specific reason why it won’t synthesise: think carefully when the code immediately following this line here elsif (updownpassenger=”1″) then will be executed. It will be executed following a positive edge or negative edge on any input in the sensitivity list, apart from clk where it will … Read more
No event will ever occur while a process is running! When a process is woken by an event, it runs to completion (“end process”) or an explicit “wait” statement, and goes to sleep. This takes, notionally, ZERO time. Which means that if you have loops in your process, they are effectively unrolled completely, and when … Read more
It looks to me like you’ve tried to instantiate lab_06 outside the architecture Behavior. Had you written end architecture Behavior;, I think the problem would have stared you in the face.