Entry type: FAQ, Entry ID: 15364459, Entry date: 03/03/2009
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What restrictions are there for active jobs when communicating with SFC 58 / SFC 59 and SFB 52 / SFB 53 via PROFIBUS DP and PROFINET IO?

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Configuration Notes:
System functions and blocks SFB52 "RDREC" / SFC59 "RD_REC" (read record) are used to read data records of a component (module) of a DP slave/PROFINET IO device. System functions and blocks SFB53 "WRREC" / SFC58 "WR_REC" (write record) are used to write data records to a component (module) of a DP slave/PROFINET IO device.

Depending on the CPU used, the number of active jobs of the system functions and blocks SFB53/SFC58 and SFB52/SFC59 is limited.

The following table provides information about how many active jobs of the system functions and blocks SFB53/SFC58 and SFB52/SFC59 your CPU supports simultaneously.
 

System function/
system block
SFB 52 "RDREC"/
SFB 53 "WRREC"
SFC 59 "RD_REC"/
SFC 58 "WR_REC"
Explanation Data record from DP slave, PROFINET IO device Data record from DP slave
IM154 (ET 200pro)
IM151 (ET 200S)
IM147 (ET 200X)
4 jobs together with SFC 58/59 4 jobs together with SFB 52/53
CPU 312, CPU 313, CPU 314
CPU 315, CPU 316
4 jobs together with SFC 58/59 4 jobs together with SFB 52/53
CPU 317, CPU 319
CPU 318-2
8 jobs together with SFC 58/59 8 jobs together with SFB 52/53
CPU 41x1) 8 jobs each per PROFIBUS DP segment and PROFINET IO system 8 jobs each per PROFIBUS DP segment and PROFINET IO system
1) The number of simultaneous jobs on external PROFIBUS DP segments or PROFINET IO systems must not exceed 32 jobs per SFC/SFB.

Example:
With a CPU 414-2DP, a maximum of 48 jobs per SFC/SFB can be executed at the same time (8 each on the two PROFIBUS DP segments that are connected to the integrated interfaces of the CPU, and 32 on external PROFIBUS DP segments and PROFINET IO systems).

Rules:

  • There are no restrictions for simultaneous jobs in the subracks (CR, ER). The SFCs run synchronously via the backplane bus. Any number of synchronous SFCs can be called.
  • If you are operating multiple communication partners on the PROFIBUS network, then please make sure that never more than the specified jobs are active at the same time. Here one SFC/SFB can run several CPU cycles long.
  • The restrictions listed in this entry for the active jobs of the system functions and blocks SFB53/SFC58 and SFB52/SFC59 also apply to the blocks that call these system functions and blocks internally. These include the blocks FM_CS, PID_FM and FMCS_PID, for example.
    Example:
    When communicating with an FM 355 (4 channels parameterized) via the FMCS_PID block, 4 read jobs are occupied.

Note:
System functions SFC58/59 are available on all CPUs.