Product : ISaGRAF V3

Date    : 5 March 1996

File    : of retain variables in IDK software.htm

Subject : support of retain variables in port pack software

Keywords: Retain


Below are some explanation on the use of RETAIN variables in ISaGRAF

V3 target. The main idea of the RETAIN variable is to copy groups of

variable values in backup memory. The following groups are defined:

Booleans, Analogs, Timers, Messages.


The string entered with application options is used to identify

where is the backup memory in the target system, and what is its

length. Corresponding entry points are grouped in TASY0RTN.C target

source file:


uchar sys_init_retain(char *arg);

/* calculates backup memory addresses for each group. */

/* The "arg" parameter is the string entered in the workbench

The current programming in the TASY0RTN.C file assumes that the

definition string is a list of (address,size) numbers expressed in

hexadecimal (without 16# prefix), separated by commas, for each

group, according to the following syntax:




uint32 sys_add_retain(uchar typ, uint32 size);

/* returns the address of a group memory block. */

/* The "Typ" parameter identifies the group. */

/* The "size" parameter indicates the space required by ISaGRAF */

/* to copy variables. Answer the backup memory address */

/* pre-calculated in sys_init_retain, */

/* or answer 0 if required size is too big. */


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