PLC 5/15 processor...Please Help

Hello All,

I have a PLC 5/15 processor and I am trying to run an analog input card (1771-IFE A) for testing purposes. I just want to see if the input card works, so I figured I could get in the input image table in RS Logix 5 and watch the decimal number change with the input I am testing.

The problem I am having is that I am not sure whether I have my PLC 5 CPU running properly. When I power up the rack, the remote light is on solid red. The CPU is communicating with the PC and I am able to go online with the processor but I don't think it is seeing the input card properly. When I go into the input image table on the left-hand side, I change the radix from binary to decimal and then the addresses listed are as follows:

I:000
I:010
I:020
I:030

Getting back to the PLC/5 though, the remote I/O LED is on solid red and the PROC LED is on solid green. The comm. LED is flashing green. The light on the input card is solid green, the fault LED is off. I would think that I should see 16 addresses listed in the input image table, as opposed to the 4 I listed above. Please advise, thanks. - O

Sounds like you're use to dealing with SLC's. With the PLC-5's You have to use BTR & BTW to get the data to and from the analog cards, even if they are located in the same rack as the processor.

If you're not familiar with Block Transfers, post back, and someone will help you over the major steps.

AB Knowledge Base is a good source of info!

http://domino.automation.rockwell.com/applications/kb/RAKB.nsf/$$Search/?OpenForm

Well it's pretty obvious you haven't done this before (maybe you're used to SLC500?), so here's the basic approach.

To talk to a 1771-IFE in the PLC5 world you need a block transfer write and a block transfer read. The values do not show up in the input table at all. I recommend that you read the manual on the 1771-IFE and the help files in RSLogix5 as a starting point.

If you can tell us a bit more about your configuration, someone may even work out the two rungs you will need for this.
Info needed: Rack, group and slot of 1771-IFE card.

If this is a test setup and you don't actually have any remote racks hooked up, then a red light on remote I/O is not suprising.

What you are seeing in the input table is the 4 rack address space (rack 0 thru 3) of the PLC5/15.

Good luck,

P.S. Gee, am I a slow typist or what? <g>

To expound on the good posts so far:

In the PLC5 the I/O image table is fixed at 1 word of input and 1 word of output image per group. A group is a logical slot location in the physical rack. Depending on how the rack is configured, a group can occuy one physical slot, two physical slots, or 1 physical slot can be occupied by two groups (1/2 slot).

When using 1 group = 1 slot addressing, each input card wastes a word in the output image table. Likewise, each output card wastes a word in the input image table. When using 1 group = 2 slot addressing the IO image table words can be conserved but then you must alternate input-output cards, that is, an input card and output card must be placed next to each other - both belong to the same group. If you were to use 32 point input cards then you must configure the rack to that two groups occupy one slot.

Because only 16 bits of input data and only 16 bits of output data are available for each group then specialty IO cards make use of block transfers to move that data to N files in the PLC.

Here a PLC 5 is shown in a 12 slot chassis. Please note that it is called a chassis, not a rack. (More on racks in a second)
Slots 0-7 are occupied by discrete IO cards.
Sltos 8 and 9 have analog cards in them.
Slot 10 is empty.
Slot 11 is occupied by a power supply.




Unlike the SLC, IO addressing in the PLC 5 is not fully dependent upon the slot the module is in. Rather a group is used.

A group can refer to 1/2 of a slot, a full slot, or two slots.
Now here is a very important point: The processor does not know what kind of chassis its in or what cards are in the chassis and it also does not know whether 1/2 slot, 1 slot, or 2 slot addressing is being used. It doesn't need to know this either. The chassis "knows" what addressing is used.

A rack is a logical rack that consists of 8 groups.

OK, lets pretend that slots 0-3 have 16pt discrete input cards and slots 4-7 have 16 pt. discrete output cards. We will talk about single slot addressing first, where a group is the same as one slot. Because a rack consists of 8 groups, our 12 slot chassis contains two racks, rack 0 and rack 1. In single slot addressing, slots 0-7 are in rack 0, and slot 8-11 are in rack 2.

Open up the program for your PLC5-15 and look at the input image and output image tables. You will find that both tables contain 32 words of data. The PLC 5/15 therefore can address up to four local racks.

Notice that there is a word in the output image table in slots occupied by input modules. There is also a word in the input image table for slots occupied by output modules.

If you chassis is configured for single slot then -
For the input card in slot 0 of the chassis, the valid addresses are I:000/0 - I:000/17 octal. The Output word exists, and you could write to it, but it wouldn't do anything. The word O:000 is wasted.

And for the the output card in slot 7 of the chassis the valid address is O:007/0 to O:007/17 octal. The input word exists, you can read and write it, but it won't do anything. The word I:007 is wasted.

If all you need is 512 points of local discrete IO then wasting the words is not a problem. But what if you need more?

Here is where we go to two slot addressing.
In two slot addressing slots 0 and 1 belong to group 1. Slots 2 and 3 belong to group 2, slots 3 and 4 belong to group 3 and so on. Each group has two modules in it. Now our twelve slot chassis becomes one rack, rack 0. In fact, we could accomodate a 16 slot chassis as one rack. But we also have to rearrange our IO modules. Slots 0 and 1 can contain 1 input module and 1 output module in any order, but you cannot place two input modules or two output modules side by side. Lest say we put the input card in slot 0 and the output card in slot 1. The address of the input card is I:000/0 thru I:000/17 and the address of the output card is O:000/0 thru O:000/17 (octal). Now we have conserved the words in the IO image table and we could address up to 1024 disrete points with your 5/15. We will need 4 16 slot chassis to do this.

But you don't want to buy that many chassis, your panel isn't that big, and besides, you only need 256 points of IO and our analog. So to maximize IO in the chassis, you decide to use 32 point IO modules in our 12 slot chassis. You configure the rack for 1/2 slot addressing. This means that each slot has two groups in it. Slots 0-3 comprise rack 0, slots 5-7 are rack 1, and 8-11 are rack 2. (OK, it can get tricky here because not all specialty modules will be capable of residing in a chassis configured this way, but in this case our analog modules play just fine here). An input module in slot 0 now has the following addresses assigned to it: I:000/0 thru I:000/17 and I:001/0 thru I:001/17.

Have you noticed that all through this we still don't have enough words in the IO image table to transfer 8 channels of analog data for each of the analog cards in slots 8 and 9? More bad news: These particualar analog modules require 59 words of configuraiton write data and send back 28 words of data on the analog values.

So to get this information back and forth from the analog modules we use a block transfer write (to send information to the module) and a block transfer read (to get information from the module)

That drawing of the PLC chassis is an actual PLC chassis. Here is a snip of the first two rungs of Ladder 2.



I'm not going to get into all of it here because it's very long. But suffice it to say that we write configuration information to the module in slot 8 of the chassis (notice that it is RACK 1, GROUP 0, Module 0 - review my previous post again if you dont understand this).

The first block transfers 59 words of data from the file N100 to configure the analog module.

The second block reads 20 words of data from the module and stors that data in file N101. The values for the analog input channels are located in this file.

You have to refer to the documentation for your particular analog module to see which words will have the analog values in them.

In the case of this particular program Ladder 2 is the first MCP. It handles all of the block transfers. Thats all it does. Ladder 3 is the second MCP, and its where the control program for the process resides. MCPs are something that you are also probably not familiar with as the SLC only supports one MCP at ladder 2.

Thanks, almost there...

Thanks all for the help, especially Alaric. I now understand how the various addressing modes of the PLC-5 processor work. I am using 1-slot addressing and my analog input card is in slot 0 of rack 0, therefore it is in group 0 and it can be assigned module 0. I made a program similar to yours as shown below. You mentioned that I would probably need to change the data files for the block transfers in order to see which words will have the analog values in them. What is your reasoning in choosing BT10:0 and BT10:1? Also, N100:0 and N101:0 for the data files? How do I determine what to assign my control blocks and data files?

The manual for the 1771-IFE gives a couple programming examples but does not show the addresses in their examples. I am referring to Pub. # 1771-6.5.115, page 30. They tell me to use enable bits as conditions on the rungs (as you did) and to use seperate control files for each block transfer (as you did). On page 67, they use N7:60 for the write block transfer data file. They don't really tell me anywhere in the manual what to assign the control and data files for the block transfer functions. If so, it isn't very obvious to me. Please advise and again thank you for all your help. - O

Greetings omars,

it looks like my distinguished colleague missed the PLC-5/15 model of your processor ... this one won't support the newer "BT" type files that he used in his example ... you'll need to stay with the older "integer-style" block transfers ...

I'm short on time ... but co-incidentally I'll be taking my students through the setup of their 1771-IFE/A modules in tomorrow's class ... if you don't have this nailed down by then, I'll try to post some examples ...

are you using CURRENT or VOLTAGE input signals? ...

are you using SINGLE-ENDED or DIFFERENTIAL wiring? ...

omars,

First off, my processor was an enhanced PLC-5. The enhanced PLC5 supports the BT file type for block transfer control blocks. But your 5/15 doesn't have the BT file type. So for your control block you will have to use an N file. In RSLogix 5 click on Help->PLC5 instruction help -> BTW for more information. The N file control block is 5 words long, so substitue N10:0 for BT:0 and N10:5 for BT:1. This also means that B10:0/EN becomes N10:0/15 and B10:1/EN becomes N10:5/15. (OK, I'm doing this from memory - so verify this in your manual.)

Alternatively, you could make seperate control files N10, N11, etc, each five words long and use 1 file for each control block needed.

I chose to use files N100 and N101 for data files in this application just to keep it simple. I already had a couple of hundred elements being used in the N7 file, and I had 35 other data files, so I just decided to make all my block transfers data files at N100 and up. You can put them where ever you want to.

I am using 1-slot addressing and my analog input card is in slot 0 of rack 0, therefore it is in group 0 and it can be assigned module 0.

Click to expand...

I know that this is just being picky, but with PLC-5s its good practice to keep our terminology straight (which is hard to do when one also works with SLCs) because in PLC5s a Rack is a logical addresses, not a physical box. It is more accurate to say the card is in slot 0 of the chassis so it is Rack 0, Goup 0, Module 0.

I mess up the terminology all the time myself and I'm always catching myself on it. But it will lead to confusion when talking to others - especially if you are using multiple 12 or 16 slot chassis.


---------------------

edit - Damn! Ron, you beat me to it before I could clear it up.

I just remembered this thread which covered much of the same material ...

OkiePC included an excellent step-by-step set of instructions which should be very helpful ...

PS edit ... sorry, Alaric ... but you're still way ahead on the scoreboard ...

Updated ladder logic

sorry bout the confusion on which version PLC 5 I have. I looked in the help file and they mention to use an integer file and that it would be 5 words long, so you are indeed right. I was even able to download the program into the CPU but I don't quite understand where to look at the data. In other words, we are reading the data into N101:0 but when I click on that file on the left side of the screen...I don't quite see the data change there. This brings up a whole host of issues.

In the manual for the input module, it says that there are jumpers on the input card that will set the modes I need but the manual I have is the 1771-IFE C...mine is a version A and the jumpers have a different layout. It has 3 row headers on it. Unfortuately, I am not quite so sure what mine is set up for....hopefully single-ended voltage mode.

Next, the programming example I found in the 1771 manual (Pub. # 1771-6.5.115, page 30) lists the BTR function block in the 1st rung and the BTW function block in the 2nd rung. The ladder logic you submitted is the other way. Does it really matter which order it appears?

Finally, my last problem has to do with how does the CPU know which channel to look at? With all the other analog modules I've done, I have always had to tell it which channel to read. It feels like I ain't giving the CPU enough information and maybe that is why it isn't giving me data in N101.

Alaric, thanks for the addressing jargon. Now I can roll my eyes at anyone who refers to a chassis as a rack. - O

this link should be the manual for the 1771-IFE/A ...



if your BTR is putting the data at N101:0 then look for the Channel 1 (first channel) input signal to be located at N101:4 ...


why there? ... see page 5-1 of the manual ... note the “word 5” location of Channel 1 ... are we having fun yet? ...

and no, the BTR/BTW rung order doesn't matter ...

gotta run ...

one more whack at it ... when you do a block transfer read, the processor brings in (at one time) a whole BLOCK of information which includes ALL of the module's analog channels ...

if you're using Single-ended wiring, then your IFE can handle up to 16 inputs ...

if you're using Differential wiring, then your IFE can handle up to 8 inputs ...

Thank you for the manual, Ron. My jumpers were not set properly of course. I went through chapter 4 and I think I have my data file set properly for the write transfer block. I included the addressing for you to look at below. It seems that the program doesn't see my data because in N100:0 and N100:1 I have them set to 3. This should make it go from 0 - 10 VDC. However, when I get in run mode, channel 1 and channel 9 corresponding addresses already have data on them in file N101 and I ain't even connecting any DC voltage to any channels at this point. When I put DC voltage on channel 1, N101:8 (corresponding to channel 5) starts giving me data from 0 - 4095 on a 0-10 VDC scale. However, if I go to channel 2, its corresponding address gives me 0-4095 but it is from 1-5 VDC. Several other channels are like that, too. It seems like the program doesn't see what I am writing to it in the N100 file. I would think that there should be no data on any address if I don't put DC voltage there.


Also, in word 1 of the data read transfer block bit 1 is high, which corresponds to an out-of-range error. Any idea