Digital Inputs - To pack or not to pack

Hi all,

My project has 8 sets of S7-315 and connected to a redundant ethernet work. I have a WinCC 6.0 with 8192 tags. The ethernet speed is 100 Mbaud and my application requires me to monitor about 160 digital tags per PLC. So, the WinCC will display more than 1000 digital bits.

My question is shall i map those digital bits in sequence in the individual PLC so that my WinCC will read 1 word or 2 words and un-pack them later again before displaying. For slower system i.e. connection through serial or modem, it is advisable to pack them in a word or 2 to optimise the reading cycle time.

But, some say it is a waste of my engineering effort to pack and un-pack the digital bits as my application is through ethernet at 100 Mbaud.

What do you think???

regards,
appleplc

It depends on what else is on the network. If there is already traffic there then I would "optimize" what you can. If its dedicated to just what you state then no need unlees it will be expanded on later.

If it is on a common network then sooner or later the traffic might get pretty high at peak times.

Just my thoughts though.

Drewcrew6

If you have even the slightest suspicion that there will be a slowdown in communications, I would consider this: It is much easier to pack the data when doing the original programming than to change it after you have discovered the problem (not to mention the duplication of effort).

via PLC protocols... only single BYTE can be transfered... so unless driver is dummy, there would not be problem with reading bit fields etc. ...maybe writing can cause sync troubles

anyway, if you have a set, which is read often, and another which is read only sometimes... it's good to optimize tranfers this way....

just test it? i better use 3rd party techs for the higher levels, so not familiar with wincc much