adccommunitymod (AutomationDirect) asked a question.
Created Date: March 25,2000
Created By: bob whalen
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On several locations, port 2 is used for modem communication. On occasion, I cannot communicate via modem. Cycling power to the unit will restore communication. On one site I have upgraded to latest firmware and put in code to reset port peroidically. Unit still required power cycling to regain communication. Most units are powered by regulated 24VDC supplies. Some projects have master/slave set up with Freewave spread spectum radios. Was never able to establish communication via port 2 with the radios. Added DCM card and communication works fine. Have used a lot of modems with other hardware and never experienced such problems. Any advice is appreciated.
Created Date: March 25,2000
Created by: bob whalen
On several locations, port 2 is used for modem communication. On occasion, I cannot communicate via modem. Cycling power to the unit will restore communication. On one site I have upgraded to latest firmware and put in code to reset port peroidically. Unit still required power cycling to regain communication. Most units are powered by regulated 24VDC supplies.
Some projects have master/slave set up with Freewave spread spectum radios. Was never able to establish communication via port 2 with the radios. Added DCM card and communication works fine.
Have used a lot of modems with other hardware and never experienced such problems.
Any advice is appreciated.
Created Date: March 28,2000
Created by: Tom Jenkins
Is your CPU in Terminal mode? We have had better success with communications when the CPU switch is in Terminal instead of Run. The unit still powers up in program run mode after a power cycle if it was running on power loss. Apparently different communications instructions are use din the two modes.
Tom Jenkins
Created Date: April 01,2000
Created by: bob whalen
I will be upgrading to the latest firmware 139. There is problem with earlier firmware. With 139, a rung of logic can be used to reset the port.
Created Date: April 02,2000
Created by: dcharv
I also had similar problems, but I think the problem was with the modem and not the PLC. To solve the problem I had to cycle power to the modem only.
Created Date: April 03,2000
Created by: bob whalen
I have PLC cycle power on modems every night. The problem I am refering to is definately firmware/hardware related. KOYO has indicated the latest firmware will correct the problem.
Created Date: April 13,2000
Created by: Mike McClanahan
The latest firmware will NOT eliminate it. It will reduce it a lot but I have been fighting this problem for over a year and I still have comm port lockouts (the problem is the port busy flag gets set) that require a power cycle to clear. The problem only occurs (at least for me) when the port is sending data and something is received at the same time. Last word I had was that Koyo was going to correct the firmware to eliminate the problem without requiring any ladder logic.
Mike
Created Date: April 13,2000
Created by: Mike McClanahan
Bob,
On the radio problem, I have not been able to make anything except Modbus work over radio with anything approaching reliability. I am currently working on a new radio that might be better but so far it is less than 50% with anything except modbus which is 100%. Go figure.
Mike
Created Date: April 13,2000
Created by: bob whalen
I have also heard later firmware to come out will fix problem without need for ladder logic.
Regarding radio communication, the DCM modules work for me withut Modbux but the extra cost per site is annoying. On next radio application, I will try the top port. I use Freewave radios and they can be set for odd parity.
Created Date: April 13,2000
Created by: Tom Jenkins
We have been running a SCADA / radio telemtry system off the bottom port of a 250 for over a year - no problems. We 're using a 4800 bps digital radio, but it is licensed frequency, not spread spectrum. The protocol is Modbus RTU. The same 250 rack has 2 DCMs as Modbus slaves being polled by two WonderWare stations, and I can plug in my laptop and monitor the program with DirectSoft at the same time.
This may sound silly, but have you checked the RTS CTS jumpers in your cabling? Does your radio need a CTS signal, or is there any software handshking that it migh be looking for? Have you increased your re-tries and your time out delays? What is your baud rate?
Created Date: April 13,2000
Created by: bob whalen
>>What is your baud rate?
Baud rate 9600 with Directnet.
Radio does not require CTS RTS connections. RTS & CTS are jumpered. 2,3 & 7 connect to radio. Same connections to either lower port on the CPU and DCM. DCM works. CPU does not.
It was a while ago when trying to get lower port to work. After several days gave up. May try it again when another project comes up requiring radios.