© Siemens Ⓟ2009
A5E02573237-01, 05/2009
1
SIMATIC
S7-1200 System Manual
Update to edition 05/2009
Product Information
In spite of efforts to ensure the accuracy and clarity in the product documentation, some of the pages in the
S7-1200
Programmable Controller System Manual
contain information that has been identified as being incomplete, incorrect or
misleading.
An interrupt event with no attached OB
When you configure the PLC, you can configure interrupt events to occur (for example, for the HSC or for edge-detection of
digital inputs). You have the option to associate the event with an interrupt OB during configuration, or you can also use an
Attach instruction in your program to associate an event with an interrupt OB.
If the interrupt event occurs but cannot find an attached OB, the following message might be written to the diagnostics
buffer: "Accepted number of pending OB 0 - events exceeded - Processing continued (no OB processing)"
When troubleshooting, check the following possible causes for this message:
● An interrupt event was enabled but not associated with an interrupt OB in the device configuration, and the user program
did not include an Attach instruction to associate the event with an interrupt OB.
● A Detach instruction in the user program removed the association with the interrupt OB.
If you receive this message, ensure that all events are correctly attached to an interrupt OB.
Booleans and Boolean arrays are not allowed for TRCV/TRCV_C and PtP instructions
The use of Boolean data or Boolean arrays is not allowed for the TRCVand TRCV_C instructions and for the point-to-point
(PtP) instructions.
GET_ERROR instruction always returns a 0 for the FLAGS byte
In the description of the of the data structure for the ERROR parameter of the GET_ERROR instruction (Section 6.2.3.3), the
description of the FLAGS byte states that a value of "1" determines that an error occurred during a call to another block.
However, the GET_ERROR instruction always returns a value of "0" for the FLAGS byte.
"Diagnostics changed" bit is not available during startup or the first scan cycle
Because the CPU does not set the "diagnostics changed" bit until the end of the first execution of the of the program cycle
OBs, your program cannot detect if there has been a diagnostic change either during the execution of the startup OBs or the
first execution of the program cycle OBs.
Attempting to force I/O on a write-protected memory card causes an error
If the user program on a write-protected memory card is being executed by the CPU, you cannot initiate or change the
forcing of I/O from a watch table because you cannot override the values in the write-protected user program. Any attempt to
force the write-protected values generates an error.
Procedure for accessing the properties of a card reader
In section 3.4.2 that describes how to create a "Program" card, the procedure is incorrect. After you expand the "SIMATIC
card reader", you must also expand the card reader device. Select the drive where you i
n
serted the memory card. Right-click
the drive to display the context menu and select "Properties". From the drop-down menu for "Card type" of the "Properties"
dialog, select "Program".
Password-protection of specific blocks or instructions
Section 3.1.4 of the S7-1200 System Manual incorrectly implies that access to the CPU can be password-protected for an
individual instruction, such as the "Set time of day/date" instruction. However, you can only password-protect access for the
complete CPU.