State Machines

State machines are built-in vif functions which tells vif sim how to behave on certain cases.

vif-sim does not know timers are supposed to works, neither for counters.

Instead of writing directly the behavior of each timer & counter blocks, Vif gives you state machines operations and the possibility to execute specific operations on each state.

Timers

TIP

An example of this state machine can be seen in the Template page

import {Timer_State_Machine} from "@vifjs/language-builder/internal/state-machines";

Timer_State_Machine has the following fields:

• start: An operation that must return a boolean telling if the timer must be started or not.
• reset: An operation that must return a boolean telling if the timer has to be reset, regardless of its state (optional).
• preset_var: The Preset Time variable, can be Time or LTime.
• timer_var: The Elapsed Time variable, can be Time or LTime.
• on_timer_elapsed: List of void operations to execute when elapsed time has reached preset time.
• on_timer_reset: List of void operations to execute when the timer has been reset.

Counters

import {Counter_State_Machine} from "@vifjs/language-builder/internal/state-machines";

Counter_State_Machine has the following fields:

• increment: An operation that must return a boolean telling if the counter has to be incremented.
• decrement: An operation that must return a boolean telling if the counter has to be decremented (optional).
• reset An operation that must return a bool telling if the counter has to be reset, regardless of its state (optional).
• preset_var: The Preset Value variable, can be any integer.
• counter_var: The Elapsed Value variable, can be any integer.
• on_counter_down: List of void operations to execute when Elapsed Value has reached Preset Value (when decrementing).
• on_counter_up: List of void operations to execute when Elapsed Value has reached Preset Value (when incrementing).
• on_counter_reset: List of void operations to execute when the counter has been reset

Example with CTU

const CTU = new Counter_State_Machine({
    // Increment on Positive edge of CU
    // Check if RESET is set, CV can't change while R is true
    increment: new Compare(
        new Internal_R_Trig(new Resolve(["#inner", "CU"])), "=", true, "AND",
        new Compare(new Resolve(["#inner", "RESET"]), "<>", true)
    ),
    decrement: undefined,
    // Reset on R
    // No edge signals, CV can't change while R is true
    reset: new Compare(new Resolve(["#inner", "RESET"]), "=", true),

    preset_var: new Resolve(["#inner", "PV"]),
    counter_var: new Resolve(["#inner", "CV"]),

    // Nothing happens when counter reached down value 
    on_counter_down: [],

    // Set Q to false when counter reset
    // Reset the CV value
    on_counter_reset: [
        new Assign(new Resolve(["#inner", "Q"]), false),
        new Internal_Reset(new Resolve(["#inner", "CV"]))
    ],

    // Set Q to true when counter reached CV
    on_counter_up: [
        new Assign(new Resolve(["#inner", "Q"]), true),
    ],
})