32Bit FIFO Q-System

[Dariusch]

Hi, Anyone know how to make a 32bit FIFO in a Q? The FIFW/FIFR does only work on 16bit. Thank you in advanced! Best regards Dariusch

[JRoss]

Build it yourself. You can use BSL or BSR commands.

[Inntele]

As a method, which is an alternative to suggested by JRoss, the 32-bit word can be divided into two 16-bit words (on high- and low-order part) and then each part synchronously write in/read from own FIFO. After reading two 16-bit words can be combined into single 32-bit word. Edited April 24, 2010 by Inntele

[Crossbow]

I've always used DMOV and a pointer (number of entries doubled) to determine where to write, and to remove I use BMOV and move the whole table back 2 registers then decrement the count. This works for floating point as well, just change DMOV to EMOV.

[Dariusch]

Hi All, Thank you for the replys. I self was thinking like Crossbow, but I can't use the BMOV with DINT!? Edit// And I want to use symbolic variables, because I want to use it as a generel Function. The BMOV will only be usefull when using Mitsu adresses direct. Edited April 25, 2010 by Dariusch

[Crossbow]

You never mentioned you were using IEC. If you're not allocating addresses, then use an array and a bunch of MOVE instructions. This would be an easy function block to write. I may give it a shot in GX Works2 when I have some free time.

[Dariusch]

Arh yes.. Sorry for the missing information at first. When having an array of 100 or even 1000 then I think making 100 or 1000 MOV instruction is not the solution. There should be a better way of doing it!? Best Regards Dariusch!

[Dariusch]

Hi again, Here is my solution of doing it. I used a FOR TO loop

[waynes]

As per crossbow, Use Z/V index registers. Much easier. Quick to index etc. No need for 100/1000 MOV instructions. Just use BMOV. Let's paint the picture a bit. Given: FIFO list with D register D100 containing the index number. D101+D102 containing the first data block (32 bits). D10 contains read/ written data. D1 is just a temp reg. for FIFR: Read the first two reg's as above (DMOV D101 D10) or wherever. Then move everything along, two spaces up * D100 K2 D1 BMOV D103 D101 D1 DECP D100 for FIFW: * D100 K2 D1 BMOV D101 D103 D1 DMOV D10 D101 INCP D100 Done.

[waynes]

BTW, I also wished there was a DFIFW/ DFIFR instuction. Wishfull thinking I suppose! :P

[Dariusch]

Hi Waynes, Yes It would be easier to make if you are using GX-Developer or If you do not whant to make a functionblock (FB) I use symbolic variable so I can not use your example. or can I Best regards Dariusch

[Crossbow]

I have been reviewing the possibility of creating a function block in GX Works2 which could make a data table of 32-bit data. It would make use of an array, which would allow a global label with no address to be used for the table destination. If I get some time to work on it, I will post an example here.

[Inntele]

See the solution of this task for IEC Developer in attachment below. DFIFO.rar

[Dariusch]

Hi Inntele, I have not yet tried your FB's but I looks simple an without to much temp.var etc. Thank you! Dariusch

[Inntele]

Hi Dariusch, Use and enjoy Using MELSEC IL language for writing functional blocks, not only provide the necessary functions with optimal code, but also allows to correct mistakes made by developers of IEC libraries. The single restriction is not possibility of array usage. Inntele