Omron SYSMAC CS Series Operation Manual page 201

I/O Communication Characteristics
Minimum I/O Response
Time
180
Note The calculation assumes the presence of only one Master Unit on the PROFI-
BUS network
The minimum response time, i.e. the time from an input on a slave device
being set to the time the output on the same slave device is set is calculated,
based on the figure below. The following assumptions are made:
• The slave device is the first one in the PROFIBUS I/O data exchange.
• The input data is available right before the internally generated cyclic
refresh request is set. In this case, a complete cyclic refresh will take
place (See section 6-5-4 Exchanging I/O Data over PROFIBUS)
PLC Cycle
Master Unit processing
PROFIBUS Cycle
Slave I/O data refresh
T Slave device Input ON (OFF) delay.
IN
T PROFIBUS I/O data exchange cycle time
PB,Cyc
(See Appendix A Bus Parameters)
T I/O Processing time in the Master Unit.
M,Proc
T Master request cyclic refresh until actual start of cyclic refresh.
M,Rrf
T PLC cycle time (See section 6-5-5 PLC Cycle Time Performance).
PLC,Cyc
T PLC cyclic refresh cycle time (See section 6-5-5).
PLC,Rf
T Slave device Output ON (OFF) delay.
OUT
The total I/O response time is the sum of all components:
T = T + T
IO IN PB,Cyc
Instruction
Execution
T T
IN PB,Cyc
T
M,proc
T
M,Rrf
ON
+ 2*T + T + T
M,Proc M,Rrf PLC,Cyc
Section 6-5
Instruction Instruction
Execution Execution
T T
PLC,Cyc OUT
T
M,proc
T
PLC,Rf
T
I/O
ON
+ T + T
PLC,Rf OUT