Siemens SIMATIC S5-90U System Manual page 326

Integral Real-Time Clock
Make certain you are aware of the following information when you make inputs into the
clock data area:
• Entries into the clock data area must be in BCD code.
• The clock runs either in the 12-hour mode or the 24-hour mode depending on how you set bit 1
in the status word. See Section 13.3 for additional information.
• The AM/PM flag (0 = AM, 1 = PM) is significant only for the 12-hour mode of the hardware
clock. Bit 7 corresponds to the following words: word 2, word 6 word 10, word 20.
In the 12-hour mode, you have to set the hours and the AM/PM flag the same way for the clock
and prompt functions.
In the 24-hour mode, if you set an AM/PM flag when you enter the values for the clock and
prompting time, then the program sets the relevant error bit.
• The clock settings you enter must be within the range defined in Table 13-2.
Variable Permissible Parameters
Seconds 0 to 59
Minutes 0 to 59
Hours in the 24-hour mode:
0 to 23
in the 12-hour mode:
for AM 1 to 12
(12 ˆ =12 o'clock noon)
for PM 81 to 92
(81 ˆ =1 o'clock PM)
0 to 999999 when
entering the operating
hours
If your inputs differ from the ones described, the operating system outputs error messages that are
displayed in the status word. The operating system resets error messages displayed in the status
word the next time you set the clock, prompt time, or the operating hours counter, if the new
settings are within the definition range. See Section 13.3.
• When you set the clock, you need to enter only the data which is required for the
implementation of the individual function. If you wish, for example, to change only the clock
function, you need not input the data for the prompt function or for the operating hours counter.
• If the clock data area is located at the end of other areas (flags, data blocks, inputs, and
outputs), the amount of clock data transferred is only as much as will fit in the area available.
Settings are not accepted if they lie outside of the available range.
• If clock data is located in the non-retentive flag area, then all the settings are lost after Power
OFF, and the time the last switch from RUN to STOP occurred is lost.
• Remember that you can determine where the clock data area is located. The word numbers and
byte numbers listed in Table 13-1 are relative.
If your clock data area is located in a data block and does not begin with DW0 but DWX, then
you must add the value X to the word number shown in Table 13-1 The same applies for the
flag, input and output areas.
Example: Your clock data area begins with DW124. The data for the time and date is then
stored in DW124 to DW127.
13-4
Table 13-2. Range Definitions for Clock Data
Variable Permissible Parameters
Day 1 to 31
Month 1 to 12
Year 0 to 99
Weekday 1 to 7
1=Sunday
2=Monday
3=Tuesday
4=Wednesday
5=Thursday
6=Friday
7=Saturday
S5-90U/S5-95U
EWA 4NEB 812 6115-02b