i `m quite new about step7 and i havea step 7 progect where a cpu using SFC 58and SFC 59writes and reads variablesto/from another CPU;SFC58/59 are locked so i don`t know where that buffer are, how can i find them?

SFCs are part of PLC's Firmware, so nobody can change their behaviour. To get help - just press F1 on SFC in Step7. As for execution details check following link (please note, that S7-300 and S7-400 are different in data order acpect):

http://support.automation.siemens.com/WW/view/en/1117740

Appendix B.

Hi automation_1,

The attached doc has the information about SFC 58 and 59.

As Aret told, with the S7-400, the SFCs 55 to 59 can also return the error information W#16#80Fx. In this case an error occurred that could not be localized.

Regards

ddg

thank you for the answer, i.m sorry buti don` tunderstand where sfc58/59 put data sent/received;
i have an s7-300

With SFC 58 "WR_REC" (write record), you transfer the data record contained in

RECORD to the addressed module.

With SFC 59 "RD_REC" (read record), you read the data record with the number

RECNUM from the addressed module.

From IOID (ID of the address area)

LADDR (Logical address of the module)

Regards

ddg

what i don t know is where iread the parameter (RECORD,LADDR,IOID,etc..) of the sfc58 that i have (i`m working on a project that i didn t), so i can understand which data are sent and where