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PLC System Start-Up and Program Test
The retentive feature in the RE switch position is determined by an entry in system data word 120
(EAF0
):
H
Bit
15
14
13
12
x
x
x
x
x = bits that determine system characteristics
(must not be changed when setting the retentive
feature!)
Figure 4-1. Relevant Bits for Setting the Retentive Feature in System Data Word 120
Bits 3, 4 and 5 of system data word 120 are set to "0" after Overall Reset of the CPU.
You can influence the retentive feature separately for flags, timers and counters by setting these
bits
•
in the restart program (OB20, OB21)
or
•
using the DISP ADDR programmer function (only permissible when the PLC is in the STOP
state!).
You can also determine the retentive feature by setting parameters in DB1 (see Section 11.3).
In the case of Overall Reset, all timers, counters and flags are reset regardless of the switch po-
sition or the contents of system data word 120.
4-6
11
10
9
8
7
6
x
x
x
x
x
x
5
4
3
2
1
0
x
x
x
0: FY 0 to FY 127 retentive and
FY 128 to FY 255 nonretentive
1: All flags retentive
0: T 0 to T 63 retentive and
T 64 to T 127 nonretentive
1: All times retentive
0: C 0 to C 63 retentive and
C 64 to C 127 nonretentive
1: All counters retentive
S5-115U Manual
SD 120
EWA 4NEB 811 6130-02b
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