How to use FIFO function using OMRON CX?

[sutton]

hi guys,

really need your help again.. i find it difficult not familiar with Omron software while my project schedule is so tight!
I would like to know how to use the FIFO function in Omron. my example logic as below:

When part loaded, sensor determined the first pitch is occupied. Then indexer motor go 2 pitches to pitch 3. At pitch 3 station start work.. After that part go another 2 pitches to unload station.
When no part loaded, station will not work when the pitch arrived. When there are no parts at all, the index conveyor will not run.

I wish to compare Data memory pitch 3 to determine whether station should work.
And if data memories are all zero my motor will not run.

I’m not familiar with Omron CX so I wonder how to work out this function. Can anyone help me, thank you.

[sutton]

I did scetch my scenario in the Omron.bmp file. please take a look. thank you so much.

[Jay Anthony]

You are misunderstanding FIFO. What you need is SFT - Shift Register. Read the document and then ask questions.

[sutton]

thank you Jay Anthony. I thought FIFO is the same with Shift Register, where the first bit go in the register will go out in the last designated area. so i was wondering if i should use SFT or ASL.

I went through your instruction manual. thank you very much. i think it's very similiar to what i want. I have some questions here, hope you help me again. thanks.

For example 3, the Starting word is HR00 and the End word is HR01.

1. When 0000 is executed, and 0001 is ON, bit '1' will be shifted from HR00 to HR01. For the next execution, the bit '1'will be carried from HR01 to HR02. I wonder where the bit shifting will to the end. where is the leftmost bit of the register?

2. OOOO is executed to shift the register. do i need to DIFU 0000?
or can i use the DIFU function to run this?

Thank you very much. im still trying hard on this Omron software. thank you.

[IO_Rack]

When 0000 is executed, and 0001 is ON, bit '1' will be shifted from HR00 to HR01.

HR00 is a 16 bit channel or word. If your shift instruction reads:

SFT
HR00
HR01

Then you have a 32 bit shift register shifting from HR00.00 through HR01.15.

For the next execution, the bit '1'will be carried from HR01 to HR02. I wonder where the bit shifting will to the end. where is the leftmost bit of the register?

It will shift no more after HR01.15. The leftmost data is lost.

OOOO is executed to shift the register. do i need to DIFU 0000?

I generally use a DIFU on the shifting (middle) leg of the SFT instruction. The state (0 or 1) of the data (first) leg will be shifted into your register when the shifting leg is executed.

[Jay Anthony]

I generally use a DIFU on the shifting (middle) leg of the SFT instruction. The state (0 or 1) of the data (first) leg will be shifted into your register when the shifting leg is executed.

I understand why you would want to differentiate the pulse driving the step input to SFT, but at Omron that is already built into the SFT function. Unfortunately, it is not the case with any of the other Omron shifting instructions.

[IO_Rack]

This is general practice here at our place of employment. The other reason we differentiate our shift is so we can immediately reset our data.

Shift is a DIFU.
Shift Reset is a DIFD driven by Shift.

Our data is latched.... Shifted into the register..... then immediately reset.

This prevents shifting the same data twice.

[chavak]

Hi Sutton,

Precicon Automation - distributors of Omron stuff in Singapore offers free user training on CX.

Give a ring and talk to either Fong Li Fen, Dexter or Wong, they offer good support.

Good Luck.