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S7-200 Tips : Handling I/O Interrupts

This program counts from 0 to 255, depending on input I0.0. If input I0.0 is set, the program counts down. If input I0.0 is not set, the program counts up.

If this input is switched on or off, an input/output interrupt routine is triggered. This I/O interrupt routine sets or resets the “count down” memory bit M0.0.

S7-200 Tips : Analog Potentiometer of the S7-200

Special Hardware Requirements:
CPU 214 or higher (with analog potentiometer), small screwdriver

This example demonstrates how to use the two analog adjustments (potentiometers, or POTs) of the SIMATIC S7-200 CPU. The positions of the potentiometers are converted into digital values between 0 and 255. The value for analog adjustment 0 is stored in special memory byte SMB28; the value for analog adjustment 1 is stored in special memory byte SMB29.
A small screwdriver is required to adjust the positioning.
This application tip demonstrates three ways to use an analog potentiometer to adjust the Preset Time (PT) of a timer.

S7-200 Tips : Edge Detection of Input Signals

This example demonstrates how to detect signal changes with the transition or edge detection functions in the S7-200. The process differentiates between off-to-on transitions (Positive Transition or Edge Up) and on-to-off transitions (Negative Transition or Edge Down). A positive transition refers to a signal change from 0 to 1 (that is, when the input is switched on). A negative transition refers to a signal change from 1 to 0 (that is, when the input is switched off).

S7-200 Tips : Time/Event Drum Example 1

This Time/Event Drum program simulates an electromechanical stepper switch or drum. A timer only, an event contact only, or a time and an event can index the EDRUM. A Jog input enables you to allow either a time or an event to advance the drum a step. The EDRUM provides 8 output coils and 7 steps that are operated on multiples of the drum time base of 1 second. Each step controls all 8 output coils.

Program Description

EDRUM Operation

The drum is enabled when the Enable/Reset input is on. Depending upon the operation of the timer and/or event, when the Enable_Reset is on and the Start input turns on, the drum begins to run. The drum begins at the step specified by the Preset input on the Time_Control subroutine and advances to the next step. When the drum advances a step, outputs are turned on or off according to the drum mask for the new step. “Ones” in the mask designate that an output be turned on. “Zeros” designate that an output is to be turned off.

S7-200 Tips : Step Sequence (Event Drum Timer)

This example program demonstrates a step sequence in which each step is followed by certain actions. The steps follow one after another, and a step is only executed when all of the conditions stipulated for it have been met. The following applies: