Siemens OP3/S7-300 312 problem

G'Day all,

I have a problem that I just can't seem to get rid of,

Equipment:

S7-300 312 Cpu with MMC.
OP3 HMI

Software:

Simatic V5.2 Step 7
Protool/Lite

With the OP3 I display and modify S5timer values by means of an Input/Output field on a screen using Tags.From a Data Block (DB5).

The problem occurs when I display the first value DB5.DBW0 in the OP3 I can write to it i.e 1.50 secs and the program will operate with that value. That is until I connect the OP3 when I check the value has changed to 4.01 secs with no input from me !?!?!?
Every time in isolation from the OP3 the value remains the same as input, 1.50 secs. Every time I connect OP3 it changes, even if I re-write value in the OP3 it changes after a period of time.

Can anyone explain??? I don't believe the problem lies in the PLC as without connecting the values is OK , it seems to lie in the OP3 but for the life of me I can't see where. In reading the manual I have detected nothing, however there does seem to possible be a connection with the reading of Data and time, for that purpose I removed the screen call etc to no avail, I have no code to read the time and date from the PLC that I know of.

Anyone any ideas????

Mylo,

If I remember correctly, I had some kind of the same problem with an S5-95U and an OP17 a few years ago. I'm not quit certain anymore but I believe that the OP uses for some reason DW0 of your DB. Try to start using DW1.

Perhaps? Just let me know

I've had the same problem.The input field changes all by it self.SO I would allso be intrested in this answer.

Hmmm can it be that you are using your value from the op directly connected to the TV bone on the timer. I dont think op 3 supports timer values directly in in/output fields. The timer value is bcd coded try using the function Bcd_I it converts bcd to int. And then replace the in/output with a input and connected the decimal value to the Bcd_I block and the to the timer. If you want to see the timer value connect a variable to BI output of the timer to a decimal outputfield on the panel. BI is the timer value in int format.

I don't think the panels can correctly hanle S5Time variables as input. The "Correct" way to handle this is to send an INT to the PLC and use the correct SFB to change it to S%Time with a bunch of restrictions along the way. I found it simpler to Send The Int and use the TON function. You can use the word as millisecnds I think. Nothing is simple with Siemens.

Hi All,

Thanks to Fritz, managed to re-address pointers to DB and use a different word to DBW0. This has worked, and the values are remaining despite power off's and re-connections.

To Bratt & Desert Dog, the OP3 does support timer values with no problems in any other area for Input/Output fields. I have been using this method for a while and this is the first time this has come up, I am using approx 160 x S5timers so as you say to carry out conversions would be quite labourous, the OP3 does not however support IEC timers so I can't use them easily, without a lot of converting.I direct the timer value to a DB word where the value is detailed as a S5TIME, then I select this within ProTool as a tag with limits etc, Input/Output field no probs.

Reading a little bit further the manual describes that for Control and response Bits Bytes n+0 and n+1 are used to synchronize the OP3 and the S7, Byte n+0 is used by the OP3 to request the current time and date from the S7 and Byte n+1 is used to detect the OP3 restarting

for this matter I don't know why they picked my only this DB to start using, however All I know is that by Not using the first word I have escaped this madness, and as DesertDog says, nothing is simple with Siemens. But it is damn good stuff usually !!!!!!!!

Nice one Fritz

Cheers all,

Mylo