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Old November 8th, 2013, 12:39 AM   #1
santisiah
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Newbie with a few questions

Hello all.. I am pretty new to programming PLC's and have a few questions. We are using Mitsubishi PLCs and HMI's and I am writing a new program. We have a lot of pumps and actuated valves we will be controlling so a lot of outputs. My question is, if we are using the internal relays in the program to control the 24VDC coils to the pumps, can I use M1 and continue with M's until whatever number I want or do I have to use the M's with Hexadecimal as I do with the outputs. These are only used for the push buttons on the HMI's and I don't have actual inputs from the "real world."

For example:

-||-, -||-, -||-, and so on..
M1 M2 M18

Hope you all understand what I am asking. Thanks for your help.
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Old November 8th, 2013, 05:26 AM   #2
dploof23
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Quote:
Originally Posted by santisiah View Post
Hello all.. I am pretty new to programming PLC's and have a few questions. We are using Mitsubishi PLCs and HMI's and I am writing a new program. We have a lot of pumps and actuated valves we will be controlling so a lot of outputs. My question is, if we are using the internal relays in the program to control the 24VDC coils to the pumps, can I use M1 and continue with M's until whatever number I want or do I have to use the M's with Hexadecimal as I do with the outputs. These are only used for the push buttons on the HMI's and I don't have actual inputs from the "real world."

For example:

-||-, -||-, -||-, and so on..
M1 M2 M18

Hope you all understand what I am asking. Thanks for your help.
Hello,
The M bits are decimal. You start at M0 and go up from there. Keep in mind, some M bits are reserved for special functions depending on the PLC type. If you look in the help menu you should find a list of special relays/registers by PLC type.

Hope this helps,
Dave
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Old November 8th, 2013, 10:36 AM   #3
santisiah
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Thanks a lot Dave. I thought so but wanted to make sure with the experts here
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Old November 8th, 2013, 11:47 AM   #4
Lancie1
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Quote:
...Can I use M1 and continue with M's until whatever number I want or do I have to use the M's with Hexadecimal as I do with the outputs.
The underlined phrase indicates that you think your "Y" outputs are Hexadecimal. They may be grouped in 16-bit words, but each Output is normally used as a single bit of a certain 16-bit word. That applies to "M" Marker bits also. Only at rare times will you need to treat Y outputs and M bits as a group (when you want to reset all bits in a word to 0, or write the same value (1 or 0) in all bits of a word).
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Old November 8th, 2013, 12:55 PM   #5
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Originally Posted by Lancie1 View Post
The underlined phrase indicates that you think your "Y" outputs are Hexadecimal. They may be grouped in 16-bit words, but each Output is normally used as a single bit of a certain 16-bit word. That applies to "M" Marker bits also. Only at rare times will you need to treat Y outputs and M bits as a group (when you want to reset all bits in a word to 0, or write the same value (1 or 0) in all bits of a word).
Lancie, I think what he is talking about is the addressing structure when programming Mitsubishi controllers. The inputs and outputs are addressed in hexadecimal, i.e. X0-XF, Y0-YF. The internal M bits used like the B3:0/1 type in AB are addressed decimally. Data registers are also decimal.

This varies by PLC type, the Q series is as I described above, but the FX I/O is addressed in octal. The M bits and Data regs are always decimal though.

Dave
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Old November 8th, 2013, 05:59 PM   #6
Lancie1
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Thanks for clearing up that he meant the address numbering system. Many older PLCs used octal and hexadecimal address numbering due to the limits of the old hardware.
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Old November 10th, 2013, 10:59 PM   #7
santisiah
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Dave is correct in what I was asking. Lancie1 thanks for your response though. I really appreciate the help.
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