Structure Of The Status Word And How To Scan It - Siemens SIMATIC S5-90U System Manual

S5-90U/S5-95U
13.3

Structure of the Status Word and How to Scan it

You can scan the status word to identify errors in the entered settings. You can deliberately change
certain bits in the status word to enable or disable transfer or read operations.
• The status word can be located in the flag area, input area or output area or in a data block. You
must define the location of the status word in DB1. See Section 13.5.
• There are four types of bits in the status word:
- Clock flags
- Operation system flags
- Operating hours counter flags
-
Prompt time flags
Table 13-3 provides you with information about the significance of the signal states of the respective
flags. Explanations about resetting of certain bits in the status word follow Table 13-3.
Table 13-3. Significance of the Bits of the Status Word
Flags Bit Read/Over-
No. write Bit ?
Clock
0 Read
flags
Read and
1
overwrite
Read and
2
overwrite
3
Operat- 4 Read and
ing overwrite
system
flags
EWA 4NEB 812 6115-02b
Signal
State
1 Error in setting entry
0 No error in setting entry
1 12-hour clock mode
0 24-hour clock mode
1 Transfer settings
0 Do not transfer settings
- irrelev. Occupied by the operating system of the PLC
1 PLC in RUN mode
The clock continually updates the clock data area
(words 0 to 17).
PLC in STOP mode
The clock updates only words 0 to 3 in the clock
data area (current time/current date). You can set
the clock by using the FORCE VAR programmer
function.
0 PLC in RUN mode
The clock updates the clock data area
(words 0 to 17).
PLC in STOP mode
The clock does not update the clock data area.
Words 0 to 3 contain the time at which the last
switch from RUN to STOP occurred.
Integral Real-Time Clock
Meaning
13-5