====== Concurrent Statements ======

===== Simultaneous IF and CASE Statement =====
<code vhdl>
    if {condition} use
         {simultaneous statement};
    [elsif {condition} use
         {simultaneous statement};]
                .
                .
                .
    [else {simultaneous statement};]
    end use;
</code>

  * appropriation like in VHDL
  * useful for piecewise defined signals

<code vhdl>
      if vin < v- use
         vout == max;
      elsif vin < v0 use
         vout == faktor_A * vin;
      elsif vin < v+ use
         vout == 0.0;
      else vout == faktor_B * vin;
      end use;
</code>

{{:vhdl-ams:new_data_types:ams_vinvout.svg?nolink&300|Example voltage curve}}

<code vhdl>
    case {expression} use
         when {choices} use
              {simultaneous statement};
        [when {choices} use
              {simultaneous statement};]
                .
                .
                .
    end case;
</code>

<callout>
=== Notes ===
If and case are used for the same appropriation like in VHDL. But at simultaneous statements the syntax differences a little.
</callout>

===== Concurrent Break Statement =====
<code vhdl>break [break_list] [on {sensitivity_clause}] [when {condition}];</code>
<note important>sensitivity_clause => digital signals, the analog part reacts on</note>

<code vhdl>
     if signal = '0' use
          v == 0.0;
     else v == vmax;
     end use;
     break on signal;
</code>

  * a concurrent break statement pauses a process
  * handling like the sequential break
  * new: sensitivity_clause -> digital event releases a break -> start analog calculations

<note important>all simultaneous statements are concurrent; exception: simultaneous procedural statement</note>

<callout>
=== Notes ===
The concurrent break breaks a process. When a digital signal occurs a reaction at the analog part, the process is stopped, the analog changes get handled and then the process goes on. The syntax is:
    break [break_list] [sensitivity_clause] [ when {condition}];
    sensitivity_clause := on {digital signals, that occur a reaction at the analog part}
For the break_list and the condition see at the sequential break.
</callout>