Siemens SIMATIC S5 Manual page 281
Distributed i/o system
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Reaction times in the ET 200 distributed I/O system
C.5.2
Calculating t
Components of t
DP
Calculating t
DP
C-14
DP
The reaction time t
comprises the following components. The constants A,
DP
B and T
depend on the baud rate (see TableC-9).
byte
t
= constant A
DP
+ (constant B + (number of I/O bytes
+ (constant B + (number of I/O bytes
+ (constant B + (number of I/O bytes
+ (constant B + (number of I/O bytes
+ ...
+ (constant B + (number of I/O bytes
Table C-9 Constants for various baud rates
Baud rate
Constant A
9.6 kbaud
64.5
19.2 kbaud
32.3
93.75 kbaud
187.5 kbaud
500 kbaud
1.5 Mbaud
0.67
3 Mbaud
0.436
6 Mbaud
0.27
12 Mbaud
0.191
The reaction time t
comprises the following components:
DP
t
= 1.6 ms
DP
+ (0.49 ms + 2
+ (0.49 ms + 1
+ (0.49 ms + 1
+ (0.49 ms + 1
t
= 3.67 ms
DP
Note
If there is at least one ET 200U distributed I/O station or S5-95U with DP
slave interface on the SINEC L2 DP bus, t
you must substitute 2 ms for any calculated result that is less than 2 ms.
T
byte
T
byte
T
byte
T
byte
T
byte
Constant B
(in ms)
(in ms)
25.6
12.8
6.6
2.62
3.3
1.31
1.6
0.49
0.164
0.085
0.044
0.024
0.022 ms)
0.022 ms)
0.022 ms)
0.022 ms)
is at least 2 ms. Consequently,
DP
))
[slave 1]
))
[slave 2]
))
[slave 3]
))
[slave 4]
))
[slave n]
T
(ms)
byte
1.15
0.573
0.118
0.059
0.022
0.00733
0.00367
0.00183
0.00092
[slave 1]
[slave 2]
[slave 3]
[slave 4]
ET 200 Distributed I/O System
EWA 4NEB 780 6000-02a
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