Siemens SIMATIC S7-200 System Manual page 40

S7-200 Programmable Controller System Manual
1 ms*
Event
1 ms*
1 ms*
1 ms*
Event
1 ms*
* Internal 1ms
Timer Update
S7-200 ensures that the firmware, the program memory, and any
expansion modules are working properly
Writing from proces s image to the outputs
Figure 4-3 Typical Scan Flow
26
Max 64 bytes data for each entity level
Reading inputs to process image input register
Main Program
Subroutine
Main Program
Subroutine
Subroutine
Subroutine
Main Program
Communication
HMI, EM277, Status Chart, PC access
Self-test diagnostics
Interrupt
Subroutine
SI Q0.0
Immediate I/O
operations