Update sequence What happens during update?

The execution of communication functions and OBs is restricted by sections. Likewise, all the dynamic data (content of the data blocks, timers, counters and flags) will be transferred to the standby CPU.

Update procedure:

1. Until the update is completed, all asynchronous SFCs which access the I/O modules (SFCs 13, 51, 52, 53, 55 to 59) initiate a ”negative” acknowledgment with the return values W#16#80C3 (SFCs 13, 55 to 59) or W#16#8085 (SFC 51). With these values are returned, the jobs should be repeated by the user program.

2. Message functions are delayed until the update is completed (see list below). 3. The execution of the OB1 and of all OBs up to priority class 15 is delayed.

With watchdog interrupts, the generation of new OB requests is inhibited, i.e. no new watchdog interrupts are stored and, thus, no new request errors occur. The system waits until the update is completed, and then generates and process up to one request per watchdog interrupt OB. The time stamp of watchdog interrupts generated with delay can not be evaluated.

4. Transfer of all data block contents which were modified since coupling. 5. The system returns a negative acknowledgment of the following

communication requests.

-- Reading/writing data records using O&M functions -- Reading data records using SSL information -- Disabling and enabling messages

-- Logon and logoff for messages -- Acknowledgement of messages

The CPU passes specific requests to other modules.

6. The system returns a negative acknowledgment of initial calls of communication functions which manipulate the contents in RAM. See also System Software for S7-300/400, System and Standard Functions. All remaining communication functions are executed with delay, after the update is completed.

7. The system disables the generation of new requests of all OBs of priority class > 15, i.e. new interrupts will not be saved and thus do not generate any request errors.

Queued interrupts are not requested again and processed unless the update is completed. The time stamp of delayed interrupts can not be evaluated.

The system no longer executes the user program or updates the I/O.

8. It generates the start event for the watchdog interrupt OB with special handling if its priority class > 15, and executes this OB as required.

Note

The watchdog interrupt OB with special handling is of particular significance in situations where you need to address certain modules or program elements within a specific time. This is a typical scenario in fail-safe systems. For details, refer to the S7-400F and S7-400FH Programmable Controllers and S7-300 Programmable Controllers, Fail--safe Signal Modules manuals.

9. Transfer of outputs and of all data block contents which were modified. Transfer of timers, counters, flags and inputs. Transfer of the diagnostics buffer content. During this data synchronization, the system interrupts the clock pulse for watchdog interrupts, delay interrupts and S7 timers. This results in the loss of any synchronism between watchdog and time-of-day interrupts.

10. Lift all restrictions. Delayed interrupts and communication functions will be executed. All OBs continue to be executed.

A constant bus cycle time compared to previous calls can no longer be guaranteed for delayed watchdog interrupt OBs.

Notice

Process alarms and diagnostics interrupts are stored by the I/O. Such interrupt requests output by distributed I/O modules will be executed when the block is re--enabled. Any such requests by central I/O modules can not be executed unless the same interrupt request did not occur again as long as the status was locked. If the PG/ES requested a master/standby changeover, the previous standby CPU assumes master mode and the previous master CPU goes into STOP when the update is completed. Both CPUs will otherwise go into RUN (redundant system status), and execute the user program in synchronism.

In the next cycle after the master/standby changeover and update, OB1 will be assigned a separate identifier. See the System Software for S7-300/400, System and Standard Functions) reference manual. For information on further special features derived from a modified configuration, refer to chapter 7.3.3.

Delayed message functions

The listed SFCs, SFBs and operating system services trigger the output of messages to all logged partners. Those functions will be delayed after the start of the update.

• SFC 17 “ALARM_SQ”, SFC 18 “ALARM_S”, SFC 107 “ALARM_DQ”, SFC 108 “ALARM_D”

• SFC 52 “WR_USMSG”

• SFB 31 “NOTIFY_8P”, SFB 33 “ALARM”, SFB 34 “ALARM_8”, SFB 35 “ALARM_8P”, SFB 36 “NOTIFY”, SFB 37 “AR_SEND”

• Statuses

• System diagnostics messages

From this time on, any requests to enable and disable messages by SFC 9 “EN_MSG” and SFC 10 “DIS_MSG” will be rejected with a negative return value.

Communication functions with derived requests

After it has received one of the requests specified below, the CPU must in turn generate communication requests and output these to other modules. Such derived requests may involve requests to read or write parameter data records from/to distributed I/O modules. These requests will be rejected until the update is completed.

• Reading/writing data records using O&M functions • Reading data records by means of SSL enquiry • Disabling and enabling messages

• Logon and logoff for messages • Acknowledgement of messages

Note

The last three of the functions listed are registered by a WinCC system, and automatically repeated when the update operation is completed.

7.3.3

Changeover to the CPU which contains the modified