Plc 5 1/2 Slot Addressing

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'Block transfer Write/read, PLC-5 (Ab)'

New Here? Please read this important info!!!
  1. Addressing Reference 1785 PLC-5 6 Figure 5 shows how to address the status file of the PLC-5 data table. Figure 6 shows a word of the status file. Figure 5 shows what is stored in each word of the status file. For more information, refer to the PLC-5 Programming Software Configuration and Maintenance Manual, publication 6200-6.4.6.
  2. Write the address based input for the signal connected to terminal 5 of the input module in slot 2 I: 2.0/5 RLL control connects input contacts and output actuators in an electrical circuit to the process.
  3. The PLC-5 and SLC-500 use a rack/slot/register/bit method for addressing the I/O modules. For example input point 15 in slot 2 of rack 1 would be addressed - I:1:2/15. The same goes for outputs. Now the legacy problems prop up. In the old days most things were octal so AB allows for different methods for addressing modules in the rack.
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Mike - (9 posts) Jan-22-02, 12:27 PM (EST)
'Block transfer Write/read, PLC-5 (Ab)'
Basically, I need to know what the specifics are of the BTW/BTR in a PLC-5. I am new to these functions, and need to appreciate the interpolation between the control bits BTxxxx and the remote I/O attached. I have tried unsuccessfully to get a decent explanation from Ab.com, and the programming help is of little use. If anybody can help me thanks v much.
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RE: Block transfer Write/read, PLC-..., Allen Nelson, Jan-22-02, (1)
RE: Block transfer Write/read, PLC-..., ianingram, Jan-23-02, (2)
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Allen Nelson - (187 posts) Jan-22-02, 01:49 PM (EST)
1. 'RE: Block transfer Write/read, PLC-5 (Ab)'

Because analog I/O has data than can just fit in a single 16-bit word, you need to have a special instruction to get the data into/out of the modules, instead of just being able to look at the data table (You probably knew that, but I'm writing for lurkers too - forgive me if I get too simplistic).

Those instructions are the Block Transfer Write (BTW) and Block Transfer Read (BTR). These instruction transfer a block of data (up to 64 words) from the PLC to a module (BTW) or from the module to the PLC (BTR).

In general, each (analog) I/O module needs a BTW/BTR pair, one for configuration, the other for data. If, for example, you have an analog input module, you would execute a BTW instruction on the powerup scan (or if data from the BTR indicated that the module had somehow lost it's configuration) to give it all the parameters that it needs to return data correctly (number of channels, format of data (2's complement, BCD), range for each channel (typically 0-4095, but some folks like to bring in the Input in engineering units))

Then, on all other scans, the BTR instruction will be executed to read all the channel data.

The BTR and BTW instruction need two blocks of register addresses in order to work: a control register, and a data register. The control register can be either a BT type (preferred), or an integer type (if you're dealing with older PLCs, or SLCs). The data register must be an integer type (although as I look at the Help file, I see an Input type shown in the example - I have no idea why they would do that!).

The control registers contains all the housekeeping info for making the instruction work - the status bits, the Rack/Slot/Group address (shown on the instruction), and other stuff that is frankly unimportant.

The data registers contain the data that is to be transferred in one block. If it's the BTW to that Analog input, it would contain the number of channels, format of data, etc. If its the BTR from the AI, it would contain some header info (typically about 5 words), followed by the current readings (scaled in the manner that you configured the module with the BTW).

Now for the easy part. In the bad old days, we had to set up the configuration by hand, making sure that all 22 words of data sent to configure an analog input were just right. RSLogix has made it easy with the IO CONFIGURATION, near the top of the project window on the left.

Double Click on IO CONFIGURATION. Double click on the Chassis Type (or right click and Add a Chassis). Configure your rack to the correct size. Point to the slot on the chassis where you will have a module, right click and select Add Module. Pick the part number. Once the part number is in the correct spot, right click and select Display Module (or just double click), and you will be presented with a dialog box for entering the Config and Data registers for both the BTW and BTRs. Enter them if you've already decided what they should be, or just pick Auto-pick (I've never been happy with the addresses they auto-assign, but that could just be me), and it will bring up a helpful window. This window allows you to just pick the setting that you want, and shows where the data will be located for programming. (If you were live with the PLC, it would show that actual raw data).

You can use the Insert Ladder Rungs button to have RSLogix make the proper ladder code for the BTW and BTR rungs. Play around with this screen and the settings and you'll get a good feel for what's going on in the BTR/BTW.

You can access this screen quickly by clicking on 'Setup Screen' on the BTR or BTW instruction.

Good luck, if you have any more specific questions, just ask,

Allen
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ianingram - (23 posts) Jan-23-02, 07:12 AM (EST)
2. 'RE: Block transfer Write/read, PLC-5 (Ab)'
try this link

(this link is mainly about analog inputs/outputs in general, but there is an example for a PLC-5 using BTW)

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There are a number of addressing schemes used by PLC manufacturers. Let’s take a quick look at how memory locations (including hardware I/O) are accessed with RSLogix 500. Along the way, let’s define some terms.

INSTRUCTION – RSLogix’s command language is comprised of “instructions”. An XIC (it looks like a normally open contact –] [– ) is an instruction. A timer is an instruction. A few of the most common instructions are described below.

BIT – an address within the PLC. It can be an input, output or internal coil, among others.

In RSLogix, there are a couple of ways to show the address of a bit. The default is:

Plc 5 1/2 Slot Addressing Machine

[type]:[word]/[bit]

For example, an address that references an output of a MicroLogix 1100 is O:0/0. That is:

O:0/5 means that it is a physical output.
O:0/5 means that it uses Slot 0 (in the case of the 1100, this output is onboard)
O:0/5 means that it is the fifth output on the PLC.

By the way, don’t get the capital “O” confused with a zero.

RUNG – A section of the PLC ladder program that terminates in an output function of some type. Just like in an electrical ladder diagram, a rung has some type of output that is turned on or turned off by the preceding entities in the rung. The first rung in a ladder program is always 0000.

HARDWIRED INPUT – a physical connection to the PLC from an input device (switch or sensor, etc.).

Plc 5 1/2 Slot Addressing Tool

Allen-Bradley uses the capital letter “I” to designate a hardwired input. An address that describes an input on an SLC 500 is I:4/0.

Similar to the output structure,

I:4/0 means that it is a physical input.
I:4/0 means that it uses Slot 4 (the 5th slot in the rack).
I:4/0 means that it is the first input on the card.

Don’t get the capital “I’s” confused with ones.

HARDWIRED OUTPUT – a physical connection from the PLC to an output device (relay or pilot light, etc.) As was said above, an address that references an output of an SLC 500 is O:5/0.

INTERNAL COIL
This is a programmable bit used to simulate a relay within the PLC. The internal coil has no connection to the outside world. It does not connect to an output card. Internal coils are used to store information. The “contacts” of this “relay” can then be used multiple times in other parts of the program.

In RSLogix, the “B3” (binary) file is commonly used for all the internal coils. There are many other words in other files that have bits you can use as internal coils, but we are going to stick with the B3 file for our application.

B3:0/0 means that it references an internal Binary file
B3:0/0 means that it uses the first word in the table
B3:0/0 means that it is the first bit in the word.

Addressing

Note that, unlike the Output and Input files, you have to use the file number in the address. In this case, the default file number is 3.

TIMER
A timer is a programmable instruction that lets you turn on or turn off bits after a preset time.

The two primary types of timers are TON for “timer on delay” and TOF for “timer off delay”.

Timers in A-B SLC and MicroLogix processors use file 4 for their timers.

T4:0 means that it references an internal Timer file
T4:0 means that it uses the first timer in the table

The address T4:0 simply refers to the timer. Each timer has bits that turn on after the timing function is complete. You can address this bit by simply putting a “/DN” after the timer address. DN stands for “done”.

For example, if timer T4:0 is a TON (timer on delay), then the bit T4:0/DN will turn on after the timer has reached its preset value.

COUNTER
A counter is a programmable instruction that lets you turn on or turn off bits after a preset count has been reached.

There are different types of counters available in the RSLogix, but the CTU (counter up) instruction covers everything we will talk about here.

Counters in A-B SLC and MicroLogix processors use file 5.

C5:0 means that it references an internal Counter file
C5:0 means that it uses the first counter in the table

The address C5:0 simply refers to the counter. Each counter has bits that turn on after the counting function is complete. You can address this bit by simply putting a “/DN” after the counter address. DN stands for “done”.

Plc 5 1/2 Slot Addressing Machines

For example, if counter C5:0 is a CTU (counter up), then the bit C5:0/DN will turn on after the counter has reached its preset value.

–] [– Normally Open Contact
When used with a hardwired input, this instruction is off until there is a voltage applied to the input. The bit address then goes high, or on, and the instruction becomes “true.” It works the same way when it has the same address as an internal coil, except that the coil must be turned on by logic in the program.

Plc 5 1/2 Slot Addressing System

Allen-Bradley calls these normally open contacts “XIC”, or “eXamine If Closed” instruction.

An XIC instruction can reference a hardwired input, a hardwired output, an internal coil or a timer done bit, among others.

–]/[– Normally Closed Contact
This is an inverted normally open contact.

When used with a hardwired input, this instruction is “true” until there is a voltage applied to the input. It then goes low, or off, and becomes “false.”

It also can be used with an internal coil, becoming true when the coil is off and becoming false when the coil is on.

Allen-Bradley calls these normally closed contacts “XIO”, or “eXamine If Open” instructions.

-( )- Output Coil
When used with a hardwired output, this function is off until the logic in the program allows it to turn on. It then becomes “true”, and will energize the device that is wired to the respective output.

If it is used as an internal coil, it will toggle the instructions associated with it. That is, it will close a normally open instruction and open a normally closed instruction.

Allen-Bradley calls these outputs “OTE”, or “OutpuT Energize”.

An OTE may be used with a hardwired output or an internal coil.

TRUE – A state that indicates an instruction is allowing logic to “flow” through it.

Also, if the logic in a rung turns on the output of the rung, then the rung is said to be true.

FALSE – Without stating the obvious, this is the opposite of true.

Excerpted from PLC Programming with RSLogix 500