PLC simple questions, just learned PLC, there are a few questions, answer

The value of the byte storage space composed of m121 m128 is fed into m21 m28.

The constants (the first address of the soft component) make up a multi-bit storage space.

For example, k1m100 is m100 m103

K2M100 is M100 M107

K3M100 is M100 M111

K4M100 is M100 M115

K5M100 is M100 M119

K6M100 is M100 M123

K7M100 is M100 M127

K8M100 is M100 M131

mov k2m121 k2m21 means to transfer m121 m128 (the bit state or bin data in it) to m21 m28, and the corresponding transmission;

m121-m21

m121-m22

m123-m23

m128-m28

mov k2m121 k2m21 means to send the value of the byte storage space composed of m121 m128 to m21 m28.

LD 20 ani m5 mov k2m121 k2m21 20 is not missing something.

1. The counter will not be reset automatically, and the reset command must be used, which can be reset RST or batch reset ZRST. The counter is a data when there is a rising edge signal at the control end, because it is the rising edge signal detected, so there must be a time when it is disconnected, if it is disconnected and reset, it can only be 0 and 1 dangling. The reset at the beginning of the program is generally M8002, reset once when the power is on, or need to reset once before counting, and carry out the operation of clearing, so that the last count has ended, but the clearing is not complete, and it has an impact on the counting, so that the program is more rigorous.

Instead of resetting the counter every scan cycle, if it is reset every scan cycle, the counter will not count.

2. I have never heard of the automatic cycle or single cycle of this step-by-step ladder diagram.

3M8002 is used as data initialization, the basic instruction programming in this practical application is also very commonly used, but you can't use some sequence control at the beginning, in practical applications, such as expansion modules, AD, DA, etc., for example, AD needs to be assigned an initial value, to specify whether AD collects current or voltage, just use LD M8002. . . to。。。For example, when communication is used, the parameters of the communication port are defined, LD M8002...

mov h81 d8120。Wait a minute. In fact, it is very commonly used.

The most common step ladder is because the program starts with set s0 to give the order of the steps a beginning.

4. The normally open contact and rising edge pulse mainly depend on how you want to operate. For example, there is a very simple start-up and stop-off procedure.

As shown in the figure, the normally open contact and rising edge pulse, X0 pressed, Y0 output and self-locking, X1 pressed, disconnected Y0 output, and released self-locking. Looks the same. But if I keep pressing x0, then the gap comes out, in the first picture, x1 presses, y0 disconnects, but x1 releases, because x0 keeps pressing, y0 outputs again and locks itself.

In the second diagram, the rising edge pulse will not, and x1 will be released and y0 will still be disconnected. Because x0 only works when it is pressed. This prevents the device from being stopped due to the pinching of the button and not being able to reset or the internal contacts of the button from sticking.

In addition, according to the action of the program, it is decided whether to run all the time with the normally open contact or to move the rising edge pulse. Wait a minute.