Help with reverse engineering code...

[geniusintraining]

OK, I know its not much but I just can't get it...

Take a look at this and help me decipher what they are doing. I see the outputs but can see how they are doing it.

The first rung is a reset
The second rung if M8000 is true then timer t0 will timeout for .5sec then reset itself.
Next when t0 is true it will add a K of 1 to do every time it goes true.
At the same time it will compare k16 to D0 then M0 is set to true??

Also move D0 to K2Y000 ?? is this the output?

also if M1 is true then move K0 to D0??

I just got back from vacation and must of took to many stupid pills when I was in the mountains I just can't see how they are making the outputs sequence the way they are and this is the complete program

I am not very good with Mitsubishi but I don't think you need to be with this..

Can someone help, many thanks

 

[Eric Nelson]

M8002 is the first scan bit, so the first rung resets D0 to zero at powerup. M8000 is the "always on" bit, so the second rung is always processed. You are correct that the timer resets itself every 1/2 second. Each time that the timer expires, it increments D0 by one. Since M0 is specified in the comparison instruction, M0 is the = bit, M1 is the > bit, and M2 is the < bit (the result of the comparison of D0 to K16). Therefore, when D0 exceeds 16, it gets reset to zero. The current value of K16 gets moved to the outputs Y0 thru Y8 with the MOV instruction (K2 means 8 bits), so you should be seeing the value represented on the outputs.

But I may be completely wrong...



-Eric

 

[geniusintraining]

But I may be completely wrong...

You never been wrong before...

Thanks Eric, that makes sense, the K2Y000 had me stumped

 

[Eric Nelson]

...the K2Y000 had me stumped

Mitsubishi actually explains it quite well in the Programming Manual...

"Bit devices can be grouped together to form bigger representations of data, for example 8 consecutive bit devices are some-times referred to as a byte. Further more, 16 consecutive bit devices are referred to as a word and 32 consecutive bit devices are a double word. The PLC identifies groups of bit devices which should be regarded as a single entity by looking for a range marker followed by a head address. This is of the form KnP where P represents the head address of the bit devices to be used. The Kn portion of the statement identifies the range of devices enclosed. “n” can be a number from the range 0 to 8. Each “n” digit actual represents 4 bit devices, i.e K1 = 4 bit devices and K8 = 32 bit devices. Hence all groups of bit
devices are divisible by 4."



-Eric

 

[Goody]

Its a nice Mitsi trick to learn.

But my 'Mr fussy head' always looks at code like this and says, why would you need the M8000 (always on bit) The second T0 can go on the next line without it.

And another tip 'GIT' - all those greyed out box's are using valuable screen area where you could display more code per page.
Grab each panel of greyed out box's and move them to the middle of the screen. They will then display a 'X' to close them. Move the other panels to the top of the screen andyou can display more screen.

Each timeyou open this project the layout will be remembered.

 

[geniusintraining]

Thanks guys