PM8240 Digital Input

[AndrewLOH]

Hi ,

Can anyone advise if the Digital Input on the PM8240 , S1,S2 and S3 ON/OFF State can be read via Modbus Register ?

I have read through the register list, Under S1,S2 and S3 State, the register is NA.

Regards

Andrew

[Yut]

You have to add Modbus slave module then link the S1, S2, S3 out to the module input set address you want to use.

[AndrewLOH]

Hi Yut,

Can you explain in details...

Regards

Andrew Loh

[sesa56307_bridg · Accepted solution]

The onboard digital input states (S1, S2, S3) should be accessible in the PM8000's default Modbus map.  In the default map, I believe register 2400 is a 16-bit bitmap of the validity for the digital inputs on the base unit (1=valid, 0=invalid), and register 2401 is a 16-bit bitmap of the status for the digital inputs on the base unit (1=ON, 0=OFF).  Since there are only three digital inputs on the base unit, they are mapped into the three lowest-order bits for S1, S2 and S3 (validity=1, status=<ON/OFF>), and the remaining 13 bits in the field are unused (validity=0).  Looking at the published documentation, I see that these registers are not described very clearly.  I will follow up to try to flag this improvement, assuming my understanding is correct.

Note also that the digital inputs on the option modules (if present) are also accessible in a similar way, at registers 2550-2557.

As per the other response here, you could also add Modbus Slave modules in the ION framework to create an (additional) custom mapping to another Modbus register.  If you want/need to do that, the user manual has some guidance on "Configuring custom Modbus data using ION Setup", and ION Setup helps with the workflow.  I would consider this a backup plan though if you can't get it working with the default map (or if you want it to appear somewhere else in the register list or with a different format).

Best regards,

David Tuckey

Firmware Architect

[Yut]

David, great idea. So the register mask will be 0000000000000001, 0000000000000010 and  0000000000000100 for all three S1, S2, and S3 at register 2400.

[nghi_bui_esec_v]

Hi Yut,

Please instruction for me methed or the connection drawing from dry contact to S1, S2, S3 of PM 8240

Thanks very much

[nghi_bui_esec_v]

Hi Sesa,

Thanks for your support. I understand. This is method execute in PME software.

But, wiring hardware form Dry Contact ACB to DI of PM8000. How i do install it? Is it power supply 24V DC external supply for this DI.

Thanks very much

[Grant_IPACS]

You need to provide external aux control power to the inputs

it is burried deep in the install manual, but it is there...

[Windsor]

Regarding the marked solution, did reading Modbus register 2401 provide the required state data or did custom mapping need to be defined?

[Charles_Murison]

Hello @Windsor 

Reading modbus address 2401 alone will result in meter returning 0xFFFF for all requests regardless of input state. You will need to read 2400 and 2401 to get the actual input states. Where results are 2400 should be 0000 0000 0000 0111, and 2401 will be 0000 0000 0000 0XYZ, where X is S3, Y is S2, Z is S1.

Regards,

Charles

[Windsor]

Hi  @Charles_Murison,

Thanks for the quick reply. Just to clarify I need to also read register 2400 even though I would do nothing with the return data?

Also do you know if the base unit digital inputs are configured as pulse counter inputs or as binary / on-off inputs?

Regards

[Charles_Murison]

Hello @Windsor ,

Correct, will need to read both registers even though you do not need 2400 information.

There are 2 modules with digital inputs, 1 is the state, ON/OFF, the second is a counter module. If digital input is default settings, a transition from OFF to ON will increment the count.

8915 is the start of registers for digital input counts.

Regards,

Charles

[Windsor]

Hi @Charles_Murison ,

Does this mean that reading the state of the digital inputs does not depend on the current processing type defined for the digital inputs?

What I want to do is simply read the state of onboard digital input 1 and am not interested in any counter data. I had thought that I would have to use ION Setup to redefine the processing type of the digital input in some way so that it was treated as an on/off input rather than as a counter input but, based on your last post, it seems that input state can be read regardless of the current processing type. Is my understanding correct?

[Charles_Murison]

Hello @Windsor,

I am not 100% I understand what you mean by "current processing type" I take this to mean the modbus request type to the meter. If this what you mean then the answer is no, the request type does matter. You will need to request at least 2 registers. What you do with the data after the request is up to you. One option would be to put a mask on the data. Many different modbus clients offer this option.

If you try to read just 1 register the meter will always return 0xFFFF, regardless of the input state.

Regards,

Charles 

[Robert_Lee]

Register 2400 is used specifically to indicate what status inputs are valid (i.e. that you can use the bits in 2400 to actually indicate which inputs are actually present).

So, if some future device were to have more available digital inputs (say 8), then register 2400 would return 0x00FF (all lower 8 bits asserted) to indicate that the device has 8 available digital inputs.  Thus when you read in 2401, you would then be able to use the lower 8 bits to indicate where those inputs are ON=1, or OFF=0.  You would ignore any bits in 2401 that were not asserted in 2400.

[Windsor]

Hi @Charles_Murison,

What I meant by "current processing type" is the input mode defined for each input in ION Setup i.e. Pulse, KYZ, A/C, IRIG-B.

I thought that because I want to know the state of digital input 1 as a binary state and not as a count, I would need to change the input mode for the input.

Is it correct that the state of the input can be read from registers 2400 and 2401 even though the input mode is set to either Pulse, KYZ, A/C or IRIG-B?

[Windsor]

Hi @Charles_Murison,

Apologies for posting the question from the previous post again but is it correct that the binary state of an input can be read from registers 2400 and 2401 even though the input mode is set to either Pulse, KYZ, A/C or IRIG-B?

I just want to be sure that I can do this before I go to customers site

[Charles_Murison]

Hello @Windsor ,

When you set a Digital Input mode to IRIG-B, the bit corresponding to that input in register 2400 will go to 0. With other settings the state will be displayed when reading the registers.

Regards,

Charles

[Windsor]

Thanks Charles/