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V130 - System bit SB90 question

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Simple question - what does system bit SB90 do?

It does not have a description in VisiLogic but it is next to SB 91 which is "I/O Exp. Module--Command buffer is full" so based on this and on my tests I think it has something to do with I/O Module too.

Why am I interested in this?

Well - I have 2 sets as mentioned in Topic description:

- the first one is on site and is working hard ;)

- the second one is on my desk and I make it suffer :P

As I tested with the one on the desk:

- SB90 is "0" when I have I/O module configured in HW configuration, everything is connected correctly and PLC is in run mode.

- SB90 is "1" when I have I/O module configured in HW configuration and disconnect I/O module during PLC running


when I have I/O module configured in HW configuration and PLC is starting (eg. after restart) with no I/O module connected

Of course when I disconnect I/O module from PLC, every DI and every AI is not read from I/O module by PLC.

My concern is that, at the moment, as I read the PLC running on site, SB90 is "1" but I get all the signals from I/O module.

I started this tests because I had problem with the PLC on the site - it had just stopped and, as guy working there told my on the phone, You could see Unitronics written on the HMI panel.

After restarting PLC (hard way - pluging the power off) everything was ok again.

So what does that SB90 really mean? If it is somehow connected with I/O module - it would really help me, if I would have known what way it is connected.

Any ideas?

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So the problemis:

I have set, as described earlier, working on site quite far away.

Moreover I have GPRS modem connected to that PLC.

The PLC has some problem and is going into stop mode from time to time with Unitronics logo and some writings on the HMI (don't know exactly what it is as I haven't seen it - just heard the description on the phone).

It look for me like there was some problem with communication between PLC and I/O module. I don't know what is the problem: is it the PLC, the module or the cable connecting them. Also I can not go there at the moment to test it for myself.

After restarting PLC (hard way - pluging the power off) everything was ok again - at least for some time.

So I figured that if I could notice the problem before the PLC would go into stop mode and restart it - it would help a little bit and PLC would work more or less fine till I can go there.

(I would upload the new program remotely via GPRS).

So is there any way I can check if the I/O module is working fine or communication has failed?

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