Siemens SIMATIC S7-400 Reference Manual page 228

Analog modules
5.18 Interrupts of analog modules
In the user program of OB 40, you can set how the programmable controller is required to
react to a limit value being surpassed or not being reached.
When OB 40 is exited, the hardware interrupt is acknowledged on the module.
Note
Note: the system does not generate a hardware interrupt if your limit setting exceeds the
overshoot or undershoot range.
Structure of the start information tag OB40_POINT_ADDR of OB 40
The limit values exceeded by the different channels are entered in the start information of OB
40 in the tag OB40_POINT_ADDR. The figure below shows the assignment of bits in DWORD
8 of local data.
31 30 29 28 27 26
Figure 5-21
(1)
(2)
(3)
(4)
(5)
Hardware interrupt triggered by "Reached end of scan cycle"
A hardware interrupt programmed to be triggered at the end of scan cycles allows you to
synchronize a process with the scan cycle of the analog input module.
A scan cycle includes the conversion of the measured values of all active channels of the
analog input module. The module processes the channels in succession. When all measured
values are successfully converted, the module reports the existence of new measurement data
at its channels to the CPU by means of an interrupt.
You can always use this interrupt to load the actual, converted analog values.
See also
Features (Page 229)
General information about parameter assignment (Page 199)
228
LB 8
25 24
1 1
1 2
Start Information of OB 40: Which event has violated limits and triggered a hardware
interrupt
Value exceeds high limit in channel 1
Value exceeds high limit in channel 0
Value exceeds low limit in channel 1
Value exceeds low limit in channel 0
Bit No.
LB 9 LB 11
.1 .0
17 16 1
1 1
3 4
Reference Manual, Ausgabe 11/2016, A5E00850736-08
0
Bit-Nr.
LD 8
S7-400 Automation System Module Data