Persistent Memory

It is important to remember that each time this function is called, data is read from the EEPROM on the Cronus. The life of an EEPROM is typically rated in the amount of read/write cycles that can be performed and although the EEPROM in the Cronus is rated for 1000's of these, you should still ensure that this function is NOT going to call in every iteration of the main loop. Never use it at the base level of the main and always ensure it is nested within an if statement which will only return TRUE for one iteration, such as event_press.

Persistence in programming means a state which remains after the process that created it has ended. For example, a word processor or paint application achieves this by saving the document to a file. The Cronus does this by writing variable values to its EEPROM (Electrically Erasable Programmable Read-Only Memory). This allows you to save the value of a variable so it can be recalled the next time the script is loaded.

There are a total of 512 persistent variables on the Cronus Zen (512 Private Variable).

Slot Persistent Variables, or SPVAR, are private to a specific memory slot. Each of the memory slots has 64 private variables, which are used to save specific values for one script. For example, Cronus Zen Slot 1 has 64 private variables which no other Slot can access, you cannot read or set the value of Slot 1's variables from Slot 4, and setting the private variables in Slot 1 will not have any effect on the private variables in any other slot. Constants have been created for use with the get and set commands for persistent variables, they are:

SPVAR_1	SPVAR_2	SPVAR_3	SPVAR_4
SPVAR_5	SPVAR_6	SPVAR_7	SPVAR_8
SPVAR_9	SPVAR_10	SPVAR_11	SPVAR_12
SPVAR_13	SPVAR_14	SPVAR_15	SPVAR_16

Cronus Zen has an additional 48 private variables bringing the total to 64, the additional private variable constants are listed below:

SPVAR_17	SPVAR_18	SPVAR_19	SPVAR_20
SPVAR_21	SPVAR_22	SPVAR_23	SPVAR_24
SPVAR_25	SPVAR_26	SPVAR_27	SPVAR_28
SPVAR_29	SPVAR_30	SPVAR_31	SPVAR_32
SPVAR_33	SPVAR_34	SPVAR_35	SPVAR_36
SPVAR_37	SPVAR_38	SPVAR_39	SPVAR_40
SPVAR_41	SPVAR_42	SPVAR_43	SPVAR_44
SPVAR_45	SPVAR_46	SPVAR_47	SPVAR_48
SPVAR_49	SPVAR_50	SPVAR_51	SPVAR_52
SPVAR_53	SPVAR_54	SPVAR_55	SPVAR_56
SPVAR_57	SPVAR_58	SPVAR_59	SPVAR_60
SPVAR_61	SPVAR_62	SPVAR_63	SPVAR_64

To retrieve the value stored in a persistent variable or to set the value of one, the following functions are available:

Function	Description	Zen	Plus
get_pvar	Returns the value stored within a persistent variable	Yes	Yes
set_pvar	Stores a value into a persistent variable	Yes	Yes

---

get_pvar

get_pvar returns the value stored in a Persistent Variable while allowing you to specify the minimum and maximum permissible value and a default value should the value stored be outside of that range. The min, max, and default parameters are mainly intended for when you are retrieving values from a Global variable, however, they must still be specified when reading the value of a private variable.

Code-Snippet

int a, b, c;

init {
    a = get_pvar(SPVAR_1, 0, 10, 5);
    b = get_pvar(SPVAR_2, 20, 40, 30);
    c = get_pvar(SPVAR_3, -30, 400, 100);
}

main {

}

Syntax

get_pvar ( <pvar_constant>, <min_value>, <max_value>, <default_value> )

Parameters

<pvar_constant> : A global or private persistent variable constant

<min_value> : The minimum permissible value

<max_value> : The maximum permissible value

<default_value> : The default value to return should the retrieved value be less then the min_value or greater than the max_value

Returns

The stored value or the default value if the stored one is out of range

---

set_pvar

set_pvar stores the specified value into a persistent variable. As GPC supports treating an int as a boolean value, the get_val command can be used to see if a controller entry simply has a value.

Code-Snippet

int a, b, c;

init {
    a = get_pvar(SPVAR_1, 0, 10, 5);
    b = get_pvar(SPVAR_2, 20, 40, 30);
    c = get_pvar(SPVAR_3, -30, 400, 100);
}

main {
    if(event_press(XB1_VIEW)){
        set_pvar(SPVAR_1, a);
        set_pvar(SPVAR_2, b);
        set_pvar(SPVAR_3, c);
    }
}

Syntax

set_pvar ( <pvar_constant> , <value> );

Parameters

<pvar_constant> : A global or private persistent variable constant.

<value> : A value to be stored

Returns

None