1756-RIO Module Block Transfers

Presently I am having an issue with the 1756-RIO module in an L63 R.17 communicating with a 1771-DB Basic Module.


Currently I have the block transfer in the RIO module configured in Auto, BTR Update 1000 ms Length 64, BTW Update 3000ms Length 64. This configuration will work for several hours and then fail. Reset of the 1771-DB will result in the block transfers working again for about 3 hours and then eventually failing.


I understand from the manual for the 1771-DB that it is really import to manage the block transfers to ensure that the BTW and BTR are not enabled at the same time.


So what I am looking to do is put the RIO modules block transfer into manual mode and manage them from the PLC. Only thing is that I am not sure how to properly configure the RIO module for this. Specifically of concern is the length of the block transfers. To configure the length in manual mode, the module manual indicates that you set this with the first 6 bits of the control word for the BTR and BTW. Doing this it seems to allow for a max of 63 words, while the module is supposed to support 64. Aside from this, what do you set the length to in the RIO configuration tool, 64 words? Does it matter?


Does anybody have any information of the proper way to configure manual block transfers in the 1756-RIO? And any experience with communicating with the 1771-DB?

first things first ...

double-check the resistors at the ends of the Remote I/O link ... the 1756-DHRIO module is a LOT pickier about being properly terminated than the older PLC-5 and SLC-500 systems ...

if the system is working OK for several hours before it acts up, then that sounds more like a network "noise" issue than problems with the block transfers ...

note that it COULD be something in the setup - but I'd definitely check those resistors first ...

I neglected to mention in my earlier post,

All the block transfers are working with the exception of the ones to the 1771-DB.

Original installation was a DHRIO module and what changed is that we converted to the RIO module to offload the BTW/BTR messages from the main CLX.

This is a new 1756-RIO module correct? Not the old DHRIO.

yes. the new RIO module.

johnreitz3303 said:

I neglected to mention in my earlier post,

All the block transfers are working with the exception of the ones to the 1771-DB.

Original installation was a DHRIO module and what changed is that we converted to the RIO module to offload the BTW/BTR messages from the main CLX.

Click to expand...

I assume from your statement, there are other RIO Modules on the same RIO Blue Hose working with no problems. Correct?

Is the DB Module in the same Rack with other Cards that the BTR/BTW are working correctly with?

Ron's advice about the Terminating Resistors still apply. They are very important.

Regarding the 64 Words issue, don't forget that zero is also a valid Word. So, 0-63 would be 64 Words.

Stu.....

Yes there are other modules on the same network that are functioning correctly.

The DB is the only block transfer module in that rack.

I will have the resistors verified, but think they are correct as this had been working on the DHRIO.

64 word thing, that is what I was considering, but did not see anything in writing that confirmed it, so I always doubt my assumptions.

johnreitz3303 said:

Yes there are other modules on the same network that are functioning correctly.

The DB is the only block transfer module in that rack.

I will have the resistors verified, but think they are correct as this had been working on the DHRIO.

64 word thing, that is what I was considering, but did not see anything in writing that confirmed it, so I always doubt my assumptions.

Click to expand...

The DB isn't in the last Rack in the RIO Chain by any chance is it?

Stu.....

no, it is in the middle.

and so is the RIO module if that matters.