Pulse Output; Understanding The S7-200 High-Speed Output Instructions - Siemens SIMATIC S7-200 System Manual

Pulse Output

L
A
D EN
F
Q
B
D
S
T
PLS
L
221 222 224

Understanding the S7-200 High-Speed Output Instructions

The CPUs each have two PTO/PWM generators to output high-speed pulse train
and pulse width modulated waveforms. One generator is assigned to digital output
point Q0.0 and the other generator is assigned to digital output point Q0.1.
The PTO/PWM generators and the process-image register share the use of Q0.0
and Q0.1. When a PTO or PWM function is active on Q0.0 or Q0.1, the PTO/PWM
generator has control of the output, and normal use of the output point is inhibited.
The output waveform is not affected by the state of the process-image register, the
forced value of the point, or execution of immediate output instructions. When the
PTO/PWM generator is inactive, control of the output reverts to the process-image
register. The process-image register determines the initial and final state of the
output waveform, causing the waveform to start and end at a high or low level.
Note
It is recommended that the process-image register for Q0.0 and Q0.1 be set to a
value of zero before enabling PTO or PWM operation.
The pulse train (PTO) function provides a square wave (50% duty cycle) output
with user control of the cycle time and the number of pulses. The pulse width
modulation (PWM) function provides a continuous, variable duty cycle output with
user control of the cycle time and the pulse width.
Each PTO/PWM generator has a control byte (8 bits), a cycle time value and pulse
width value (unsigned 16-bit values), and a pulse count value (unsigned 32-bit
value). These values are all stored in designated locations of the special memory
(SM) area. Once these special memory bit locations have been set up to select the
desired operation, the operation is invoked by executing the Pulse Output
instruction (PLS). This instruction causes the S7-200 to read the SM locations and
program the PTO/PWM generator accordingly.
S7-200 Programmable Controller System Manual
A5E00066097-02
The Pulse Output instruction examines the special
memory bits for the pulse output (Q0.0 or Q0.1). The
PLS
ENO
pulse operation defined by the special memory bits is
then invoked.
Operands:
Data Types: WORD
Q
Pulse Output Ranges Q0.0 through Q0.1
226
SIMATIC Instructions
Q Constant (0 or 1)
9-49