Technical Data, Scan On-Load Times
S5-95U, Second Serial Interface
Interrupt reaction time
The interrupt reaction time increases by a maximum of 2.3 ms for all functions that are executable at
the SI2 interface (exception:
”
Compress block
”
programmer function; Calculation of interrupt
reaction times S5-90U/S5-95U System Manual, Section 10.3) .
The total interrupt reaction time T
Itot
(up to 1st STEP 5 operation in OB3) is calculated as follows:
T
Itot
=
T
Ibas
+
T
ISI1
+
T
ISI2
T
Itot
=
Total interrupt reaction time
T
Ibas
=
Basic reaction time
T
ISI1
=
Interrupt reaction time at SI1
T
ISI2
=
Interrupt reaction time at SI2
Example:
If an OP is connected to SI1 and a programmer to SI2, the total interrupt reaction time is
as follows: T
Itot
=
0.6 ms
*
+ 0.4 ms
*
+ 1 ms= 2 ms
-------
*
Values taken from: S5-90U/S5-95U System Manual, Section 10.3, Table 10-8
PLC scan cycle load
In the case of programmer/operator panel functions:
For current programmer/operator panel functions, the scan on-load time is function-dependent and
can therefore not be specified universally.
S5-95U as SINEC L1 slave or point-to-point slave/master:
PLC scan cycle load depends on the number of bus cycles during the PLC scan cycle. The bus
cycle is asynchronous to the PLC scan cycle.
In order to define the PLC scan cycle load you must
1.
Compute the PLC load time per bus cycle
2.
Compute the time for a bus cycle (to estimate the percentage by which the PLC scan time
increases as a result of SINEC L1 communications)
1. Compute PLC load time
PLC load time
Bus cycle
= x
· T
B*
+
T
REA**
+
T
REC
+
T
S
x
=
Number of frames in a bus cycle
T
B
=
Basic load time (must always be accounted for, i.e. irrespective of whether the slave is
addressed or not):
1ms per SINEC L1 frame
T
REA
=
Slave response time, PLC addressed as slave (irrespective of whether net data
available) :
1.5 ms
T
REC
=
Receive time in the case of reception of max. net data (64 bytes) :
1 ms
T
S
=
Send time in the case of transmission of max. net data (64 bytes):
1 ms
*
For S5-95U used as a point-to-point master: T
B
=1.5 ms per SINEC L1 frame.
**
For S5-95U as point-to-point master T
REA
is omitted in the equation.
Example:
S5-95U is SINEC L1 slave
Number of frames
=
15
Net data
”
receive
”
=
64 bytes
Net data
”
send
”
=
64 bytes
PLC load time
Bus cycle
= 15·
1 ms+1.5 ms+1 ms+1 ms = 18.5 ms
-------------
E-2
EWA 4NEB 812 6095-02
