Siemens Simatic S7-200 System Manual page 306

Instruction Set
Communication Port Interrupts
The serial communications port of the programmable logic controller can be controlled by the
ladder logic or statement list program. This mode of operating the communications port is
called Freeport mode. In Freeport mode, your program defines the baud rate, bits per
character, parity, and protocol. The receive and transmit interrupts are available to facilitate
your program-controlled communications. Refer to the transmit/receive instructions for more
information.
I/O Interrupts
I/O interrupts include rising/falling edge interrupts, high-speed counter interrupts, and pulse
train output interrupts. The CPU can generate an interrupt on rising and/or falling edges of an
input. See Table 10-14 for the inputs available for the interrupts. The rising edge and the
falling edge events can be captured for each of these input points. These rising/falling edge
events can be used to signify an error condition that must receive immediate attention when
the event happens.
Table 10-14
I/O Interrupts
The high-speed counter interrupts allow you to respond to conditions such as the current
value reaching the preset value, a change in counting direction that might correspond to a
reversal in the direction in which a shaft is turning, or an external reset of the counter. Each
of these high-speed counter events allows action to be taken in real time in response to
high-speed events that cannot be controlled at programmable logic controller scan speeds.
The pulse train output interrupts provide immediate notification of completion of outputting
the prescribed number of pulses. A typical use of pulse train outputs is stepper motor control.
You can enable each of the above interrupts by attaching an interrupt routine to the related
I/O event.
10-118
Rising/Falling Edge Interrupts Supported
CPU 212
I/O Points
CPU 214 CPU 215
I0.0 I0.0 to I0.3 I0.0 to I0.3
S7-200 Programmable Controller System Manual
C79000-G7076-C230-02
CPU 216
I0.0 to I0.3