Assigning A Flag Bit To A Message - Siemens SIMATIC S5 TD 390 Manuel

8.3

Assigning a Flag Bit to a Message

Message and Each message DB is assigned three flag bytes in the parametric DB.
flag bits
These bytes contain the flag bits which must be set in the program to
select a specific message. The flag bytes are evaluated in the order they
are given in the group of three, irrespective of the chronology in which
the flag bits were set. The figure below shows the assignment of flag bits
to messages.
Message DBxy
DW
MESSAGE 1
0
10
MESSAGE 2
20
MESSAGE 3
150
MESSAGE 16
230
MESSAGE 24
Flag bit in user Activate the flag bit at the points in your program where you want to
program
display a message.
Example:
C DB xy
select message
A I 1.1
A I 1.3
= Q 1.0
= F 0.5
TD 390
C79000–K8576–C292–01
Creating a PLC Program for the TD 390
Flag byte
Flag bit
0
0.7
0.6
0.5
.
.
0.4
.
.
0.3
.
.
.
. 0.2
0.1
.
0.0
DB with message
MESSAGE 3 is entered in the TD 390 message
buffer
1 2
1.7
2.7
1.0 2.0
Cont'd
8-3