Technical data

Table Of Contents
SFCs for Handling the System Clock
System Software for S7-300/400 System and Standard Functions - Volume 1/2
A5E00709327-01
5-3
5.3 Synchronizing Slave Clocks with SFC 48 "SNC_RTCB"
Definition: Synchronizing Slave Clocks
Synchronizing slave clocks refers to the transmission of the date and time from the
master clock of a bus segment (for example, the S7-400 K-bus, MPI, or S7
backplane bus) to all clock slaves of the bus segment.
Description
With SFC 48 "SNC_RTCB" (synchronize real time clocks) you synchronize all the
slave clocks on a bus segment, independent of the configured synchronization
interval. Successful synchronization is only possible when SFC 48 is called on a
CPU whose real-time clock was assigned the master clock function for at least one
bus segment. You assign the relevant parameters with STEP 7.
Parameter Declaration Data Type Memory Area Description
RET_VAL OUTPUT INT I, Q, M, D, L If an error occurs during the execution of the
function, the return value contains an error
code.
Error Information
Error Code (W#16#...) Explanation
0000 No error occurred during synchronization.
0001 The existing clock was not assigned the master clock function for
any of the bus segments.
8xyy General error codes, see Evaluating Errors with Output Parameter
RET_VAL