where are bitwise AND, OR and XOR used

[sinha_nsit]

I know what these are, but do not know why these are there!
Can somebody give one application of these functions (bitwise operations).
Unless somebody knows the area of application, he will never try to use it.

[Dan Fritz]

Boolean operations can be used for a lot of things. Here's an example:

Let's say you connect a set of 8 swiches to the User Macro Inputs (UI0-UI7). The switches identify what pallet is loaded, with each pallet having a different binary code on the switches. Now, in your macro, you could "decode" the binary number by looking at macro variable #1032. Keep in mind that #1032 is the SUM of 16 inputs, and we only need to use 8.

Now, suppose we need to include something in our program to be certain that we've got the right pallet loaded. Suppose this pallet has the binary number "27". The number 27 is binary 00011011, so we need to look at only the lower 8 bits of #1032 for the binary number 27. All other binary numbers in this range should be rejected as the wrong pallet.

#100=#1032 AND 255 Set #100 to be only the lower 8 bits of 16-bit number #1032
IF[[#100 XOR 27] = 0] GOTO
GOTO1
#3000=(WRONG PALLET)
N1
(go ahead and run your part)
M30

Sure, you could use the BIN operator here also, but with bitwise operators, you could select any single bits or any combination of bits to make a decision in your program.

Boolean operations are most useful for I/O logic (an input or an output have only two states), but can be used for "true/false" comparisons also.

[sinha_nsit]

Thanks for the useful and interesting information.
Since such an application is new to me, I would like to know how physical connections of external switches are done with the CNC. Is some interface device needed, which is connected to RS232C port of CNC?

If possible, please attach the scanned copy of the description of the interface signals (#1000 series and #1100 series). I do have Operator's Manual, but detailed description is not there. I do not have Connection Manual, where detailed description is given.

[sinha_nsit]

Dan,
I know I asked an stupid question. Actually, I knew nothing about interfacing at that time. Now, I understand it a little bit.

The only doubt I have now is, how the binary signals for pallet numbers are sent?

The simplest way would be to have 8 switches for each pallet, and the switch setting (in binary) would indicate the pallet number.

Additionally, a pallet may have a limit switch to sense whether or not it is loaded. And, the binary signals would be sent only if the limit switch is pressed.

If so, physical connection, through a ribbon cable (8 signal wires and one common wire) between the terminal strip of the I/O module and each pallet would be needed. This would make the whole arrangement clumsy, and might cause interference in a moving system.

Am I correct?

It may again be a stupid question for an expert like you, but I would appreciate an answer.

[Dan Fritz]

Here is the way it's usually done:

First determine what the maximum number of different pallets there will be. Two pallets can be sensed with just one switch (on or off). Four pallets with two switches, eight pallets with 3 switches, sixteen pallets with 4 switches, etc. There is no need to use 8 switches unless you have 256 pallets. In addition to the "binary number" switch array, you might use an additional switch that just confirms that the pallet is down and locked. That switch would be actuated by all the pallets.

The switches are usually mounted on the stationary part of the machine, underneith where the pallets would be clamped down. The pallets would simply have little "Buttons" on the bottom that would line up with the swtiches. When a pallet is locked down, a certain combination of switches would be actuated by the buttons on the pallet. The array of switches would be permanently wired to the the I/O board with a cable.

A more sophisticated pallet system might use barcoding or an RF (Radio Frequency) tag to pass more information to the machine than just a pallet number.