Holding Registers and Integer compatibility in Micrologix 1400?

Mowgli86

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Join Date
Aug 2013
Location
UK
Posts
19
Hi,

My first post here, although I have been using these pages a lot over the last few weeks as I'm trying to get more familiar with PLC work. There has been a lot of useful info, but I couldn't find the answer to this question.

I am a complete novice and don't really know what I'm talking about, so please go easy!

I am trying to use a Micrologix (A) PLC to control a Parker SSD 890 Drive. The drive only has a Modbus communications card, and the ML only does Ethernet/IP. I know the sensible option is to buy an Ethernet/IP card for the drive and then use Messages to communicate, but I do need to get this working quickly, and can't wait for spare parts. We also have a Red Lion G3 HMI unit which seems able to communicate with both the PLC and Drive, in their respective languages. I thought, naively, that I could send certain integers to tags in the HMI, use the internal programming there to map them over to the tags which are sent to the drive. But now I see that the tags being sent to the drive are holding registers, not integers, so the HMI programming can't do this mapping.

Does anyone know which data format in the PLC is compatible with holding registers which are being sent over Modbus? Are Long Integers compatible with holding registers?

I'd be very grateful for any pointers, especially those which aren't 'go and buy the right equipment'!

Thanks!

Mowgli
 
Ah - I think I've sorted it. Not using the Programming part of the Red Lion software, but using a data block to do the mapping in the communications part. it's as if it was designed for it!
 
In general, a Modbus Holding Register is equivalent to an ordinary 16-bit Signed Integer in the A-B logic controller world.

The MicroLogix 1400 controller can use Modbus RTU protocol on either of its serial ports. It can be either a Modbus RTU Master or a Modbus RTU Slave.

Only the MicroLogix 1400 Series B controller can use Modbus/TCP protocol on the Ethernet port. The MicroLogix 1400 Series A cannot, and it cannot be upgraded to Series B.

If you're up and running with the G3 and its data blocks, that's great. I just wanted to provide some comments on what the MicroLogix 1400 supports with regard to Modbus protocols.
 
Thanks - if I had been able to use Modbus/TCP that would have perhaps been easier, but then I might not have been able to use RSLinx for programming. I may buy the Series B next time just to have the option.
 
Thanks - if I had been able to use Modbus/TCP that would have perhaps been easier, but then I might not have been able to use RSLinx for programming. I may buy the Series B next time just to have the option.
you can do modbus tcp and programming or ethernet/ip simultaneously on the 1400 ethernet port.
 

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