RIO 1791-n4c2 question

[sparx 0]

Hello and good day! Lookin for some experienced/pro advice. I've been doin this about 15yrs, but I'm not exactly sure about this one. Confidence level is medium I have a rio network setup and running. The other day I installed an additional 1791-n4c2 on the network. As we were rushed to get this done, I forgot to tie in the comm wires. As the 504 was down to change the G file, I never noticed, and the guyz were chappin at the bit to get goin - I put the 504 into run. So all was fine, but I then noticed no communication lines to the device. So I noticed the adjacent n4c2 and 8ar were working and communicating fine and so I connected comm wires and the comm lite lit up. So my initial reaction iz that if a rio device failz - the the other devices continue to function. Yeh, I knew that. right? that iz true? So I went to look at the i/o table and noticed that it has some values. But wait, the values are not functioning??? oh yeah - the device (n4c2) has to be configured (dumb a$$). ok, but this is two dayz later now. So I have the settingz figured out. I have a move instruction set to dump the value into the output table when the bit iz toggled. The all important question iz -Will It accept the input and function, without shutting down the processor??? perhaps the n4c2 will need to be power cycled - still not a problem. I just don't need the hassle of having to restart the process - plus all the pissy guyz - you know how that iz :] So whadda ya think? I'm 90% sure all will go fine. none of the inputz/outputz are referenced in the program, so there wont be conflictz that way. Both power and comm lites are green for GO! anybody have any experience with this. itz more a rio question i guess. cheerz

[Ken Roach 194]

I think you're on the right track. When you send a configuration Block Transfer Write (BTW) instruction to the module, it should go into operation and will have no effect on the SLC controller, the 1747-SN scanner, or the other modules on the RIO network. For those of you reading along at home, the 1791 Block I/O series were a distributed I/O system based on "blue hose" RIO protocol that preceded the development of FLEX I/O in the mid-1990s. I used it extensively on large machine systems in the sawmill industry. Because it was so widely distributed it was vital to monitor the Rack Fault bits in the controller so you were certain that a module was connected, powered, and configured before you used the input data in your program. The 1791-N4C2 in particular is an analog combo module with four input channels and two current-loop output channels. My recollection based on a quick glance at the manual is that it can use either discrete mode or Block Transfers to move the data to the controller. If you're using a Block Transfer Read, you should see that Word 0, Bit 15 is true right now; that's the "Power Up" bit that indicates the module has been power cycled and has not received a configuration Block Transfer Write command yet. Once you send a BTW with the configuration data in it, the module will start reporting input data and pushing output current. Some devices that rely on configuration block transfers don't give you a steady green LED until they get the configuration, like the 1771-IFE or 1771-OFEx modules. The Block I/O is more like a regular RIO adapter; you get a steady green COMM LED when it's being scanned in RUN mode even if the configuration block transfer has not yet been sent.

[sparx 0]

thanks Ken. I am using discrete transfer az it mentioned in the manual, max scaling iz available. I also recall that yes - monitoring of fault bit essential to verify realtime data. 1791 block i/o is networking with 1747-SN card. at present time all word 0 bit are false. As I mentioned, using discrete transfer. I will take a look at mo table and view itz status. will reply later. have a good weekend all.

[Ken Roach 194]

Thanks for the clarification about using Discrete mode. As you'll see in the User Manual (1791-UM005) on page 3-6, the Discrete mode gives you just four Words of input data; one per analog channel. There is no detailed status word when you use Discrete mode like there is when you use Block Transfer mode, therefore there is no Power-Up bit available. The Configuration word is still used in Discrete Mode. You set Word 0 of the output image to configure the module, using the same bit patterns described for the Configuration Word in the block-transfer section of the user manual, on page 4-4. If that word is all zeroes, the module will function in default mode, which is 0-10 V inputs with a minimum value of -10,000 and a maximum of +10,000 (as you have mentioned).