GE 90-30 slowing down COMM_REQ to reduce data usage

Set-up. Main plant PLC (GE 90-30) talks to 5 remote PLC(GE 90-30) over DSL line. at remote plants, each have cellular modems to connect to the internet. they all have cisco frewall with VPN connection established. GE 90-30PLC which are using COMM_REQ SRTP channel commands. and these are communicating over ethernet through cellular modems. the data plan on the cellular modem has a limit of 5GB only.


The PLC have been communicating GOOD with the only exception that it is using a lot of DATA (maybe around 9-20 Mb/hr which puts it close to 5 gb/month or more.
how to slow it down.?

Regards
Suraj

If you have set up the channel to be continuous then words 10 and 11 of the COMMREQ that sets up the SRTP channel define the frequency of reads or writes on that channel. Word ten specifies the time increment (10 mS, 100 mS, 1 second, 1 minute, 1 hour) and word eleven specifies the number of time increments between each read or write.

If you set the channel up for a single read or write then the time between each execution of the COMMREQ is the frequency for the data transfer.

Thanks Steve,
Initially these were talking over the radio (Trango 900 Mhz radio) but due to frequent comm dropout due to no clear line of sight, it was decided to go through cellular modem.
here is the config of command block.
Word 1: 17
word2:0
word3:8
word4:3000
word5:0
word6:0
word7:2003
word8: 1
word9:1
word10:3 (seconds)
word11:0 (initially when it was on radio word11:0, then I changed it to 5 (sec)to see if it reduces data usage.)
word12:100
word13: 76
word14:1001
word15: 76
word16:1001
word17: 96
word18:1
word19:4
and then there is IP address.
At 5 seconds i didnt see any decrease in data usage.
today i will increase word 11 to see if it shows reduction in data usage.

do i have to do anything on the remote PLC as the cellular modem is on that end. On the main PLC which initiates communication it goes through DSL line for which i have no data limit.

Thankyou for your quick reply.
Regards

Hi Steve.
(This logic was written by some other guy)

for each remote PLC, there are 4 such command blocks; 2 to read bits and registers and 2 to write bits and registers to remote PLC.

and there is a continous Counter (UPCTR) that counts from 0 to 4 and then resets back to 0 and go on.. Comm_success bit turns it on for each counter.

at 0 Read bit is enabled which executes the respective cmd block
at 1 Read Regs is enabled which executes the respective cmd block
at 2 Write bit is enabled which executes the respective cmd block
at 3 Write Regs is enabled which executes the respective cmd block..

and this goes on continously.. so I guess if i slow down this counter, would it slow down the data usage.
Regards
Suraj

The value of 1 in Word 9 means that that the read command is to be executed once so the timing set up in words 10 and 11 serve as a timeout period. The frequency of exectution is controlled by the rate at which the UPCTR instruction increments. Your idea to slow down the UPCTR should work.

For details on how this all works get GFK-0582 from here:
DO225: Series 90 Serial Communication User's Manual

Hi Steve,
when i increased the counter to 8, the comreq status went to 1 and the counter stopped at 5.
whats the best way to slow counter, by adding a timer to each counter output with respect to the logic i had said earlier

Russ; I am using this manual GFK-1514B for reference right now Chapter 3
Regards
Suraj

Without being able to see the program its hard to say. I don't think you should increase the preset of the counter. There will be a contact at the upper left hand node of the counter instrruction. Each time it transitions from off to on, the counter will increment by one. You need to figure out what makes that contact transition from off to on.
You hinted in an earlier post that successful execution of the COMMREQ instruction makes the counter increment. Try making the COMMREQ success bit start a timer and when the timer reaches its preset value bump the counter.

Thanks Steve,
I will try that.. Right now i have put a 3 sec timer on each the 4 enable bits that moves the respective read and write registers into the command block.
it seems to be working now. i have communication now, Tomorrow i will be able to check the data usage on Verizon and see how it did.
Regards

Thank you Steve for all your help and suggestions. I am now able to slow down the communications to about 30 Mb/day from 200 Mb/day with a 4 sec timer delay. And the communication holds up pretty good.
Thank you again for all your help.

I'm glad to hear you got it working to your satisfaction and that I was able to help.