Siemens Simatic S7 Series

Program instructions
7.2 Clock
S7-200 SMART
System Manual, 09/2015, A5E03822230-AC
165
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
Invalid dates are not accepted. If you enter February 30, for example, a time
-of-day non-
fatal
error will occur (0007H).
Do not use the READ_RTC / SET_RTC instructions 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, system flag bit
SM4.3 is set, indicating that two simultaneous acces
ses 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 for
the year 2000, the year is represented as 00. However, user programs that
use the year's
value must take into account the two
-digit representation.
Leap year is correctly handled through year 2099.