Siemens SIMATIC S7 - Clock; Read and Set Real-Time Clock

Program instructions
7.2 Clock
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
185
7.2
Clock
7.2.1
Read and set real-time clock
LAD / FBD
STL
Description
TODR T
The Read real-time clock instruction reads the current time and date from the CPU
and loads it in an 8 byte Time buffer starting at byte address T.
TODW T
The Set real-time clock instruction writes a new time and date to the CPU using the
8 byte Time buffer data that is assigned by T.
Non-fatal errors with ENO = 0
SM bits affected
• 0006H Indirect address
• 0007H T data error
None
Input
Data type
Operand
T
BYTE
IB, QB, VB, MB, SMB, SB, LB, *VD, *LD, *AC
Note
READ_RTC, SET_RTC programming tips
These instructions do not accept Invalid dates. If you enter February 30, for example, a time
-
of
-day non-fatal error occurs (0007H).
Do not use the READ_RTC / SET_RTC i
nstructions in both the main program and in an
interrupt routine. A READ_RTC / SET_RTC instruction in an interrupt routine cannot execute
while another READ_RTC / SET_RTC instruction is executing. In this case, the CPU sets
system flag bit SM4.3, indicatin
g that two simultaneous accesses to the clock were
attempted resulting in a T data error (non
-fatal error 0007H).
The time
-of-day clock in the CPU uses only the least significant two digits for the year, so 00
represents the year 2000. User programs that u
se the year's value must take into account
the two
-digit representation.
The CPU handles leap year correctly through year 2099.