Experimental Physics and
Industrial Control System

Dirk Zimoch <[email protected]> · Wed, 12 Nov 2008 15:40:53 +0100

Hi,

This should not happen. I will check this. Please send me the configuration line
from your startup script.

When no output record processes, nothing should be sent to the PLC. However, if
some output records process and other output records have never processed, the
unprocessed records send 0. For that reason, I suggest to process every S7plc
output record at initialization with field(PINI,"YES"). The first package is
sent to the PLC after all PINI records have finished.

Note that it is not possible to sent "half" buffers. When the IOC boots, the
buffer is filled with 0. Whenever an output record processes, it writes to the
buffer. Periodically, the driver checks if any output record has been processed.
If yes, the whole buffer (including uninitialized parts) is sent to the PLC. If
no, nothing is sent.

Dirk

Silver wrote:
> hi, all:
> 
>   I am using s7-plc driver written by Dirk, while I met a problem. while the driver connetcs to plc, it will clear the data buffer of PLC to zero. the database is like following:
> record(ao,"$(id):cmd_gap_pos_cmd") 
> {
>     field(DESC,"command gap position")
>     field(SCAN, "Passive")
>     field(DTYP,"S7plc")
>     field(OUT,"@Siemens_S7: 0/2 'T=UINT32'")
>     field(LINR,"LINEAR")
>     field(LOPR,0)
>     field(HOPR,4294967295)
>     field(EGUL,0)
>     field(EGUF,429496.7295)
>     field(DRVL,17.0000)
>     field(DRVH,140.0000)
>     field(EGU,"mm")	
>     field(PREC,"4") 
> }
>   
>   I remember the Passive mode will not write data to PLC when connecting, but why it can't work? Can anyone give some hints? thanks a lot for your help.
> 
> Best regards
> Geyang  2008-11-05
> 
> 
> 

-- 
Dr. Dirk Zimoch
Paul Scherrer Institut, WBGB/006
5232 Villigen PSI, Switzerland
Phone +41 56 310 5182

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System