Product:    ISaGRAF 4.1x
Date: 24-August-2001
File: Access to system variables from the target.htm
Subject: How to access to system variables (or to other variables from their VA) from an IO driver
Keywords: System variables - VA - I/O drivers- BF_xxx macros

_____________________________________________________________________________________________

Here is the way to access system variables from an I/O driver.
Note that:

The system variables VAs are defined in the file: dsy0sdef.h: look for defines begining with ISA_SYSVA_
or look at the end of this FAQ (not all listed).

To access to them:

You must first get the pointer to the begining of the variable table (real-time database of the Virtual machine).
When you are in an IO driver you have the pointer to a channel of your device: call it pChannel.

strRtIoChan* pChannel;
uchar *curBfData = NULL;
pChannel = pRtIoSplDvc->pRtIoChan;
curBfData = (uchar*)pChannel->pvKerData - pChannel->KerVa;

With curBfData you get the pointer to the first variable, then with the following macros you can get the variables you want:

BF_BOOL(BfData,va)
BF_SINT(BfData,va)
BF_DINT(BfData,va)
BF_REAL(BfData,va)
BF_TIME(BfData,va)

with 'va' equals to the Virtual Address of the variable you want to access.

Example: BF_DINT(curBfData,ISA_SYSVA_TCYCURRENT)

__________________________________________________________________________________________

list of system variables

In the R/W column:

Variable Name TYPE    R/W Meaning

ISA_SYSVA_CCEXEC

 BOOL W Execute one cycle when application is in cycle to cycle mode

ISA_SYSVA_CYCLECNT

 DINT R Cycle  counter

ISA_SYSVA_KVBPERR

 BOOL R/W Kernel variable binding production error

ISA_SYSVA_KVBCERR

 BOOL R/W Kernel variable binding consumption error

ISA_SYSVA_RESMODE

 SINT R Resource execution mode

ISA_SYSVA_RESNAME

 STRING R Resource name (max length=255)

ISA_SYSVA_SCANCNT

 DINT R Input scan counter

ISA_SYSVA_TCYCYCTIME

 TIME R/W Programmed cycle time

ISA_SYSVA_TCYCURRENT

 TIME

R

 Current cycle time

ISA_SYSVA_TCYMAXIMUM

 TIME

R

 Maximum cycle time since last start

ISA_SYSVA_TCYOVERFLOW

 DINT

R

 Number of cycle overflows

ISA_SYSVA_WNGARG

 DINT R Warning Argument

ISA_SYSVA_WNGCMPTNM

 STRING R Warning component name

ISA_SYSVA_WNGCMD

 SINT R/W Warning command. Set it to 1 to get next warning

ISA_SYSVA_WNGNUM

 DINT R Warning Number

_____________________________________________________________________________________________

Copyright © 1999-2009 ICS Triplex ISaGRAF Inc. All rights reserved.