Siemens simatic s7-400 FM 450-1 - Page 91

Modes, settings, parameters and commands
8.12 Initiating a process interrupt
Counter module FM 450-1
Manual, 02/2014, A5E03648739-02
91
Hardware interrupt OB, OB 4x
If a hardware interrupt occurs, the user program is interrupted, the data are transferred from
the module to the start information of the OB 4x and the OB 4x is called. The hardware
interrupt is acknowledged by quitting the OB 4x.
If no OB 4x is programmed the CPU goes into STOP. If you then switch back to RUN, the
hardware interrupt requirements are deleted.
Start information
The temporary variable OB4x_POINT_ADDR is described in the start information of the
OB4x.
The OB4x_POINT_ADDR variable (bytes 8 - 11) consists of four bytes. The information on
the event that initiated the hardware interrupt is entered into these four bytes. The following
table shows which bits are set for which interrupt. All bits not listed have no meaning and are
zero.
Byte
Bit
Significance: Interrupt in the case of...
Counter 1
0
0
Opening the gate
1
Closing the gate
2
Overflow
3
Underflow
4
Reaching comparison value 1 in the up direction
5
Reaching comparison value 1 in the down direction
6
Reaching comparison value 2 in the up direction
7
Reaching comparison value 2 in the down direction
1
0
Zero crossing
5
Setting of the counter
Counter 2
2
0
Opening the gate
1
Closing the gate
2
Overflow
3
Underflow
4 Reaching comparison value 1 in the up direction
5
Reaching comparison value 1 in the down direction
6 Reaching comparison value 2 in the up direction
7
Reaching comparison value 2 in the down direction
3
0
Zero crossing
5
Setting of the counter