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Entry type: FAQ Entry ID: 19215608, Entry date: 07/16/2012

How can you read out the identification data (the serial number of the MMC, for example) with the SFC 51 in STEP 7 V5.5?

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With the SFC 51 "RDSYSST" (read system status) you can read out system status lists or excerpts of system status lists. More detailed information about parameterizing the SFC 51 and about error evaluation is available in the STEP 7 Online Help. For this you mark the SFC 51 in the SIMATIC Manager and press the "F1" key.

You need the following parameterization in order to read out the serial number of the MMC:

  • SSL ID W#16#011C "Identification of a component"
  • Index W#16#0008 "Serial number of the memory card"

Fig. 01 shows the call and parameters of the SFC 51 "RDSYSST".

Fig. 01

The table below specifies which other identification data can be read out depending on the CPU type and firmware version. For this you use SFC 51 and SSL ID W#16#011C.

Index Designation S7-300/C7 S7-400
W#16#0001 Name of automation system Firmware version V2.2 onwards Yes
W#16#0002 Name of CPU Firmware version V2.2 onwards Yes
W#16#0003 Facility ID of CPU Firmware version V2.2 onwards Yes
W#16#0004 Copyright entry Firmware version V2.2 onwards Yes
W#16#0005 Serial number of CPU Firmware version V2.2 onwards As from MLFB 6ES741x-xxx04-0AB0
W#16#0006 Reserved for operating system - -
W#16#0007 CPU type name - Yes
W#16#0008 Serial number of the MMC Firmware version V2.0 onwards
(CPU317: as from firmware version V2.1)
Firmware version V5 onwards

Notes on the output of SFC51 with a Field PG
When you read out the serial number of an MMC with SFC51 on the Field PG, the output data of the SFC51 is different to the serial number of the MMC. The reason for this system-specific behavior is that the digits of the hexadecimal code have been resorted through processing of the SFC51. For the output of a serial number, 1342498713, for example, with the SFC51 you get the value 99E70450Hex .

The table below explains how the SFC51 output is made after resorting of the digits.

Serial number of the MMC: 1342498713
Hex code of the serial number: 5 0 0 4 E 7 9 9
Designation of the digits: a1 a2 b1 b2 c1 c2 d1 d2
Digits are resorted with SFC51: d1 d2 c1 c2 b1 b2 a1 a2
Display with SFC 51: 9 9 E 7 0 4 5 0

There is a unique serial number saved on the memory cards of S7-400 version V5 onwards and the MC serial number can be read out using any SIMATIC S7-400 CPU with firmware V5.0 onwards.

Fig. 02

Further Information
The following documents contain further information about the memory cards and the system status list.

  • For MC:
    device manual "S7-400 Automation System, CPU Specifications"
    (Entry ID: 23904550),
  • For SSL:
    reference manual "System and Standard Functions for S7-300/400"
    (Entry ID: 1214574).

Additional Keywords
Memory card, RAM card, FLASH card, FEPROM card, System status list

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